US20050003675A1 - Dielectric etch chamber with expanded process window - Google Patents

Abstract

A capacitively coupled reactor for plasma etch processing of substrates at subatmospheric pressures includes a chamber body defining a processing volume, a lid provided upon the chamber body, the lid being a first electrode, a substrate support provided in the processing volume and comprising a second electrode, a radio frequency source coupled at least to one of the first and second electrodes, a process gas inlet configured to deliver process gas into the processing volume, and an evacuation pump system having pumping capacity of at least 1600 liters/minute. The greater pumping capacity controls residency time of the process gases so as to regulate the degree of dissociation into more reactive species.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This is a continuation of application Ser. No. 10/254,969, filed Sep. 24,2002 entitled DIELECTRIC ETCH CHAMBER WITH EXPANDED PROCESS WINDOW by James Carducci, et al., which is a divisional of application Ser. No. 09/704,972, filed Nov. 1, 2000 entitled DIELECTRIC ETCH CHAMBER WITH EXPANDED PROCESS WINDOW by James Carducci, et al., now abandoned.
BACKGROUND OF THE DISCLOSUREFIELD OF THE INVENTION
• The present invention relates generally to a semiconductor wafer processing apparatus. More specifically, the invention relates to a dielectric etch processing chamber having improved thermal and by-product management capabilities, improved control of gaseous species residence time, and an expanded process window including high flow rates and low operating pressures.
BACKGROUND OF THE INVENTION
• One challenge facing all forms of semiconductor processing is the industry wide progression towards decreasing feature sizes resulting in rapidly shrinking critical dimensions. Current design rules have feature sizes of less than about 0.18 microns and feature sizes below about 0.1 microns are being developed.
• Another challenge facing semiconductor processing is the trend towards smaller footprint devices. One approach to achieving a smaller device footprint is to build the device structure vertically and in some devices, fabricating portions of the device in the substrate itself.
• These challenges generate a need for processing applications capable of fabricating high aspect ratio structures and structures with critical dimensions approaching the sub-0.1 micron range.
• In view of these challenges, minimizing particulate contamination during the myriad processing sequences used to fabricate an electronic device is critical. Chamber components are selected and processes are performed in reduced atmospheres to assist in reducing and managing particles that may be present and/or generated in the processing environment. Of particular importance is the management of films that form within the process chamber during wafer processing.
• Films deposited within the processing chamber are major contributors to the total particulate concentrations found within the process chamber. Films typically form on exposed chamber and process kit components during a wide variety of semiconductor processing applications.
• During dielectric etch processes, for example, some of the material removed from the layer exposed to the etchant is exhausted from the processing chamber. However, some etch reaction by-products form deposits on exposed chamber surfaces and on surfaces of the etched structure.
• The deposits on chamber surfaces increase in thickness as the process cycles are repeated and additional wafers are processed. As the deposit thickness increases, so too does the internal stresses associated with the deposit. Additional stresses are created in these deposits due to differences in thermal expansion rates between the deposit and the chamber surfaces. Conventional etch chambers lack appropriate thermal management techniques to reduce thermally induced stresses between accumulated deposits and chamber components. Eventually, the stresses can cause the deposits to crack, consequently releasing particles into the chamber environment. These film particles may impinge upon the wafer surface, typically creating a defect in the circuit structure on the wafer.
• Control of deposit formation on the etch structure is also a critical process consideration. In high aspect ratio dielectric etch processes, for example, the formation of a thin sidewall layer or passivation layer is desired to help maintain sidewall profile control as the depth of the etched feature increases. As feature sizes decrease, however, sidewall profile control becomes increasingly more difficult and possibly unfeasible using conventional plasma etch chambers. Decreasing critical dimensions require increasingly refined control of an expanded range of etch process chemistry parameters not provided by conventional etch chambers.
• Therefore, there is a need for a dielectric etch processing apparatus with the capability of providing expanded processing capabilities with improved process parameter control that enables advanced feature dielectric etch processes.
SUMMARY OF INVENTION
• The disadvantages associated with the prior art etch chambers and the challenges posed by advanced dielectric etch processes are overcome by embodiments of the present invention of a thermally controlled plasma etch chamber having an expanded process window and improved byproduct management capabilities. The inventive process chamber is generally a capacitively coupled plasma source chamber and, more specifically, a capacitively coupled chamber operating in an RIE mode and MERIE mode.
• An embodiment of an apparatus according to the present invention comprises a capacitively coupled reactor for plasma etch processing of substrates at subatmospheric pressures having a chamber body defining a processing volume, a lid provided upon the chamber body, the lid being a first electrode, a substrate support provided in the processing volume and comprising a second electrode, a radio frequency source coupled at least to one of the first and second electrodes, a process gas inlet configured to deliver process gas into the processing volume, and an evacuation pump system having pumping capacity of at least 1600 liters/minute. The greater pumping capacity controls residency time of the process gases so as to regulate the degree of dissociation into more reactive species, such as free fluorine.
BRIEF DESCRIPTION OF DRAWINGS
• The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
• FIG. 1 is a cross-sectional schematic view of a parallel plate semiconductor wafer processing system;
• FIG. 2 is a cross-sectional schematic view of a semiconductor wafer processing system illustrating an embodiment of an upper and a lower liner according to the present invention;
• FIG. 3A is a plan view of a lid assembly having the first liner ofFIG. 2;
• FIG. 3B is a plan view of another lid assembly;
• FIG. 4 is a partially exploded elevation of the lid assembly of eitherFIG. 3A or3B;
• FIG. 5 is plan view of the second liner ofFIG. 2;
• FIG. 6 is a cross-sectional view of the second liner ofFIG. 5 taken along section line5-5;
• FIGS. 7a-7fare various embodiments of a gas inlet;
• FIG. 8 is a plan view of the ceiling interior surface corresponding toFIG. 2.
• FIG. 9 is a plan view of an individual mini-gas distribution plate of the invention having angled gas inlets providing a preferred vortex pattern of gas spray.
• FIG. 10 is a cross-sectional cut-away view corresponding toFIG. 9.
• FIG. 11 illustrates an alternative spray pattern corresponding toFIG. 4.
• FIG. 12 is an enlarged cut-away cross-sectional view corresponding toFIG. 2.
• FIGS. 13 and 14 are top and sectional views, respectively, of a plate in which has been formed a texture consisting of square protrusions.
• FIG. 15 is a sectional view of an alternative to the embodiment ofFIG. 14 in which the sides of the square depressions are formed at an oblique angle.
• FIGS. 16 and 17 are top and sectional views, respectively, of an alternative embodiment in which the depressions are hemispherical in shape.
• FIGS. 18 and 19 are perspective and sectional views, respectively, of a texture consisting of a series of circumferential grooves in a cylindrical side wall liner.
• FIG. 20 is a perspective view of a cylindrical liner having both circumferential and longitudinal grooves.
• FIG. 21 is a plan view of a plasma etching chamber with an exhaust manifold having an annular, U-shaped magnet system embedded within an annular protrusion according to the invention.
• FIG. 22 is a detail of the magnet system and annular protrusions in theFIG. 21 chamber.
• FIG. 23 is a perspective view of an annular, U-shaped magnet system with magnetic poles facing radially outward.
• FIG. 24 is a perspective view of a magnet system whose magnets and pole pieces are interchanged relative to the embodiment ofFIG. 23.
• FIG. 25 is a perspective view of an annular, U-shaped magnet system with magnetic poles facing radially inward.
• FIG. 26 is a perspective view of a magnet system whose magnets and pole pieces are interchanged relative to the embodiment ofFIG. 25.
• FIG. 27 is a detailed plan view of an exhaust manifold having two annular magnets respectively embedded within two annular protrusions according to the invention.
• FIG. 28 is a cross-section partial schematic view of an alternative embodiment of the present invention in a capacitively coupled, magnetically enhanced reactive ion etch (MERIE) processing system;
• FIG. 29 is a cross-section partial schematic view of an alternative embodiment of the present invention in a parallel plate etch processing system;
• FIG. 30 is a cross-section partial schematic view of an alternative embodiment of the present invention in a, capacitively coupled, magnetically enhanced reactive ion etch (MERIE) processing system generated by a rotating magnetic field;
• FIG. 31 is a cross-section partial schematic view of an alternative embodiment of the present invention in an etch processing system having an RF driven inductive member;
• FIG. 32 is a cross-sectional schematic view of another semiconductor wafer processing system having a chamber liner with a showerhead gas distribution system and an inductive coil;
• FIGS. 33A and 33B are cross-section views of a representative self-aligned contact feature;
• FIGS. 34A and 34B are cross-section views of a representative high aspect ratio contact feature;
• FIGS. 35A and 35B are cross-section views of a representative via feature;
• FIGS. 36A and 36B are cross-section views of a representative mask open feature;
• FIGS. 37A and 37B are cross-section views of a representative spacer feature; and
• FIGS. 38A and 38B are cross-section views of a representative dual damascene feature.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.DETAILED DESCRIPTION OF INVENTION
• Exemplary Processing System
• FIG. 1 illustrates an embodiment of the processing apparatus improvements of the present invention in anexemplary processing chamber100 for processing asubstrate10, such as a semiconductor wafer. The invention will be described below initially with reference to embodiments as used in theexemplary processing system50 ofFIG. 1. However, it should be understood that the description of the inventive features applies to the alternative chamber configurations such as theetch chamber configurations2800 to3200 described below with reference to FIGS.28 to32. Embodiments of the present invention are particularly advantageous in plasma etch chambers configured for oxide and dielectric etch processes.
• An embodiment of the present invention is illustrated inprocessing system50 ofFIG. 1.Processing system50 comprises aprocessing chamber100, agas panel105, acomputer controller140, a heat exchanger or temperature controlledfluid source121, anRF source150, apump109, anexhaust system110 and a coolinggas system107.
• Theprocessing chamber100 includes acircumferential sidewall106, abottom wall108 and alid assembly102 that together define achamber volume110. Asubstrate support124 is disposed onbottom wall108 for supporting thesubstrate10. Generally, thechamber volume110 is divided into aprocess volume112—the upper region of the chamber—and apumping volume114—the lower region of the chamber.Chamber liner104, illustrated as afirst liner134 and asecond liner118, is disposed adjacent towalls106,108 andlid102. In an embodiment described in greater detail below,chamber liner104 includes a plasma confinement means52 for confining a plasma withinprocess volume112.
• Theprocessing chamber100 is provided with aslit valve139 or access port for transferring substrates from a common loadlock or transfer area into theprocessing region112. A robot53 (shown in phantom inFIG. 1) is used to transfer substrates in and out ofprocessing region112. A slit valve door (not shown) provides a vacuum seal of theslit valve opening139. Aliner door70 could be a vertically actuated via apneumatic motor72 as illustrated inFIG. 1 to cover the opening in thechamber liner104 adjacent theslit valve opening139.
• Substrate support124 may use electrostatic force or mechanical clamping force to ensure thesubstrate10 remains in place during processing. If electrostatic force is used,substrate support124 includeselectrostatic chuck55. Alift pin assembly155 comprises lift pins160a,bthat are elevated through holes in theelectrostatic chuck55 by apneumatic lift mechanism170. Therobot53 places thesubstrate10 on the lift pins160a,b,and thepneumatic lift mechanism170 lowers thesubstrate10 onto the receiving surface ofelectrostatic chuck55. After thesubstrate10 is placed on theelectrostatic chuck55 and prior to conducting a process, anelectrode105 embedded in theelectrostatic chuck55 is electrically biased with respect to thesubstrate10 to electrostatically hold thesubstrate10.
• On completion of the process, thepneumatic lift mechanism170 raises the lift pins160a,bto raise thesubstrate10 off the receiving surface ofelectrostatic chuck55, allowing thesubstrate10 to be removed by therobot53. Before raising the lift pins160a,b,thesubstrate10 is electrically decoupled or de-chucked by dissipating the residual electrical charges holding thesubstrate10 to theelectrostatic chuck55.
• In the embodiment illustrated inFIG. 1,electrostatic chuck55 is formed from a dielectric that envelops and electrically isolates theelectrode105 from thesubstrate10. Preferably, the dielectric is a ceramic material, such as Al₂O₃, AlN, BN, Si, SiO₂, Si₃N₄, TiO₂, ZrO₂, codierite, mullite, or mixtures and compounds thereof. In one embodiment, theelectrostatic chuck55 is formed from a high thermal conductivity ceramic material with a resistivity selected for optimal performance in the temperature range that thesubstrate10 is maintained. For example, resistivity in the range of between about 5 e¹⁰Ω-cm to about 5 e¹³Ω-cm, for example, have been used where substrate temperatures in the range of between about −20° C. to about 50° C. are desired.
• Anelectrode105 disposed withinsubstrate support124 couples RF energy intoprocess volume112. RF energy fromRF source150 is coupled toelectrode105 viaimpedance matching circuitry151.Electrode105 may be formed from an electrically conducting material, such as a metal, for example, aluminum, copper, molybdenum or mixtures thereof. Generally,electrode105 has a robust construction that allows coupling of up to about 5000 Watts of RF power fromRF generator150. The exact amount of RF power coupled throughrobust electrode105 varies depending upon the particular etch process conducted withinetch chamber100.
• Abacking plate161 is disposed adjacent toelectrostatic chuck55. Thebacking plate161 has internal cooling channels supplied with temperature controlled fluid fromheat exchanger121 viainlet163. The temperature controlled fluid, such as for example, an ethylene glycol and de-ionized water mixture, circulates through the conduits in the cooling plate. Preferably theelectrostatic chuck55 is attached to thebacking plate161 so as to maximize heat transfer from theelectrostatic chuck55 to the backing plate cooling channels and thence to the temperature controlled fluid.
• In another aspect of the present invention, thebacking plate161 is bonded or joined to theelectrostatic chuck55 by a bond layer made from a material having high thermal conductivity. The bond layer can comprise, for example a metal, such as aluminum, copper, iron, molybdenum, titanium, tungsten or alloys thereof, such as for example, titanium diboride. The bond layer eliminates use of bolts for securing theelectrostatic chuck55 to thecooling plate161 and consequently reduces mechanical stresses on theelectrostatic chuck55. Also, the bond layer has a homogeneous composition that provides more uniform heat transfer rates across thesubstrate10, and reduces the differences in thermal impedances that occur at the interface between the coolingplate161 and theelectrostatic chuck55.
• Preferably, the bond layer is ductile and compliant to provide an interface that absorbs the thermal stresses arising from the thermal expansion mismatch between theelectrostatic chuck55 and thecooling plate161 without damaging theelectrostatic chuck55. While a bonded joint provides uniform heat transfer rates, it is often difficult for a bonded joint to withstand the thermal stresses arising from differences in thermal expansion coefficients of dissimilar materials, such as theelectrostatic chuck55 and thecooling plate161. An exemplary bond layer is made from a ductile and compliant material that can flex and absorb thermal stresses that arise from the difference in thermal expansion coefficients of theelectrostatic chuck55 and thecooling plate161. One suitable bonding material consists of a high bond strength, pressure sensitive acrylic adhesive, loaded with titanium diboride and applied to an expanded aluminum carrier. The combination of filler, expanded metal and embossed surface enhances the conformability and thermal performance of the bond.
• The temperature of thesubstrate10 is controlled by stabilizing the temperature of theelectrostatic chuck55 and providing a cooling gas, such as helium, from coolinggas source107 to channels formed by the back of thesubstrate10 and grooves formed on the receiving surface ofelectrostatic chuck55. The cooling gas facilitates heat transfer between thesubstrate10 and theelectrostatic chuck55. The space between the backside of thewafer10 and the receiving surface of theelectrostatic chuck55 is preferably divided into two zones—an inner zone and an outer zone.Separate flow controllers107_o, and107_iare used to provide independent cooling gas flow control to the outer and inner zones, respectively. Typically, the desired amount of cooling gas is measured in pressure, generally, in Torr.
• Separate zone controllers107_iand107_oallow the zones to be maintained at the same pressure or at different pressures. Adjusting the pressure in the inner and outer zones leads to a corresponding adjustment in the temperature at the center and edge of thesubstrate10. Thus, by adjusting the pressure of the inner and outer zones the temperature profile across thesubstrate10 is controlled. The temperature across thesubstrate10 may be adjusted to compensate for the specific temperature requirements of a particular etch process. For example, the temperature across the substrate may be uniform from center to edge, have a higher edge temperature than center temperature or have a higher center temperature than edge temperature.
• During plasma processes, thesubstrate10 is heated by plasma in the chamber and the dual zone cooling gas control is used to adjust the substrate temperature. Typically,substrate10 is maintained in a temperature range of between about −20 to about 150 degrees Celsius with a preferred operating range of about 15 to about 20 degrees Celsius. The inner and outer cooling gas zones can also be operated to induce a thermal gradient acrosssubstrate10. For example, the inner zone and the outer zone cooling gas pressures can be adjusted so that the temperature in the center of thesubstrate10 is greater than or less than the temperature at the edge of thesubstrate10. In addition, the inner and outer cooling gas zones may be adjusted so that the temperature difference across the center to edge of thesubstrate 10 is about 5 C or where the temperature between the center and edge remains nearly constant.
• The components ofsubstrate support124 including coolingplate161, anelectrostatic chuck55, dual zone backside cooling gas androbust electrode105 cooperatively operate to remove heat generated during plasma processing operations conducted inchamber100. The thermal management and temperature control features enable processing operations that employ higher RF powers and higher magnetic fields (for chambers using magnetically enhanced processing) for longer process times because the temperature ofsubstrate10 can be efficiently controlled even during processes combining both RF power levels above 2500 W and magnetic fields greater than 100 G. The temperature control and thermal management capabilities ofetch chamber100 are furthered by the direct temperature control feature ofliners118 and134 described below in section II entitled “Temperature Controlled Chamber Liner.”
• Gas panel105 includes process gas supplies and flow control valves which under the control ofcomputer controller140 provide process gases to processchamber100. Process gases fromgas panel105 are provided via piping103 throughlid assembly102 to a plurality of gas inlets ornozzles350. A plurality ofnozzles350 are distributed across thelid assembly102 for providing process gases intoprocessing volume112 as described in greater detail below in section III entitled “Thermally differentiated Gas Supply System”.
• In operation, asemiconductor substrate10 is placed on thesubstrate support124 and gaseous components are supplied from thegas panel105 to theprocess chamber100 throughnozzles350 to form a desired gas composition in theprocessing volume112. The gas composition is ignited into a plasma in theprocess chamber100 by applying RF power from theRF generator150 to impedance matchingcircuitry151 to theelectrode105. The plasma formed from the gas composition is in contact with the temperature controlled surfaces of thelid assembly102 and theliner104.
• The pressure within theprocess chamber100 is controlled using athrottle valve8 situated between thechamber volume110 and avacuum pump109. In a preferred embodiment, thepump109 provides a pumping capacity of greater than about 1000 liters per second, preferably between about 1,400 to 2,000 liters per second, and more preferably about 1,600 liter per second. Pump109 may be a single high capacity vacuum pump or a combination of a vacuum pump and a turbo pump. Under the control ofcontroller140, thepump109 and thethrottle valve8 cooperatively operate to provide an advantageously expanded pressure and gas flow rate plasma etch processing regime. In a preferred embodiment, the plasma etch chamber is a thermally controlled etch chamber capable of performing both magnetically enhanced reactive ion etching (MERIE) and reactive ion etching (RIE) etch processes in a low pressure—high total gas flow regime, such as for example, a total gas flow of more than about 350 sccm and a chamber pressure of less than about 80 mT. Preferably, an embodiment of a process chamber according to the present invention enables chamber pressures below about 50 mT with total flow rates of about 1000 sccm.
• Plasma etch chambers having embodiments of the present invention are capable of low pressure—low flow dielectric etch processes such as for example, spacer etching and mask open etching generally conducted at pressures of between about 10 mT to about 80 mT with total gas flow rates of from about 40 sccm to about 150 sccm. Plasma etch chambers having embodiments of the present invention are also capable of high-pressure high flow rate dielectric etch processes such as, for example, C₄F₈and C₂F₆based etch processes conducted at pressures of between about 150 mT to about 300 mT and total gas flow rates of between about 350 sccm to about 700 sccm. Plasma etch chambers having embodiments of the present invention are also capable of high total gas flow—low chamber pressure etch processes such as, for example, C₄F₆and CH₂F₃based etching of self aligned and high aspect ratio contacts at pressures of from between about 10 mT to about 120 mT and total gas flow rates of between about 600 sccm to about 900 sccm.
• Additionally, plasma etch chambers having embodiments of the present invention enable etch processes in a variety of processing regimes, such as for example, an etch process regime with a total gas flow ranging from about 120 sccm to about 400 sccm at a chamber pressure ranging from about 70 mT to about 120 mT; an etch processing regime with a total gas flow ranging from about 100 sccm to about 450 sccm at chamber pressures ranging from about 20 mT to about 70 mT; and an etch processing regime having total gas flows ranging from about 300 sccm to about 800 sccm at chamber pressures ranging from about 20 mT to about 70 mT. Section VII below entitled “Chamber Process Window And Representative Critical Dielectric Etch Processes” provides additional details of the improved oxide and dielectric etch process window enabled by plasma etch chambers having embodiments of the present invention.
• Acontroller140 comprising a central processing unit (CPU)144, amemory142, and supportcircuits146 for theCPU144 is coupled to the various components of theprocess chamber100 to facilitate control of the chamber. To facilitate control of the chamber as described above, theCPU144 may be one of any form of general purpose computer processors that can be used in an industrial setting for controlling the various chamber components and even other processors in a processing system where computer controlled chamber components are utilized. Thememory142 is coupled to theCPU144. Thememory142, or computer readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk drive, hard disk, or any other form of digital storage, local or remote. Thesupport circuits146 are coupled to theCPU144 for supporting the processor in a conventional manner.Support circuits146 include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. A process, such as the etch process, is generally stored in thememory142, typically as a software routine. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by theCPU144.
• The software routine executes a process, such as an etch process, to operate thechamber100 to perform the steps of the process. When executed by theCPU144, the software routine transforms the general purpose computer into a specific process computer (controller)140 that controls the chamber operation to perform the steps of the process. Although embodiments of the present invention are discussed as being implemented as a software routine, some or all of the method steps that are discussed herein may be performed in hardware as well as by the software controller. As such, the invention may be implemented in software and executed by a computer system, in hardware as an application-specific integrated circuit or other type of hardware implementation, or in a combination of software and hardware.
• Temperature Controlled Chamber Liner
• Temperature controlled chamber components, such as achamber liner104 andlid assembly102, for use in an etch processing system such asprocessing system50 may be better appreciated by reference toFIGS. 2-6. Embodiments of the present invention also provide methods for controlling the temperature of chamber components, to substantially improve adhesion of deposits formed on these chamber components.
• FIG. 2 is a cross sectional view of one embodiment of anetch chamber100 of the present invention having achamber liner104. Theetch chamber100 is configured as a parallel plate etch reactor. Generally, thechamber liner104 comprises a first (first)liner134, a second (second)liner118, or both afirst liner134 and asecond liner118. Disposed within eachchamber liner104 is at least one passage formed at least partially therein having an inlet and outlet adapted to flow a fluid through the passage from a temperature controlled, fluid supply system, such asheat exchanger121. To facilitate description of the liner of the present invention, an embodiment of the liner of the present invention will be described as having a first134 and a second118 liner. One of ordinary skill will appreciate that a single piece, removable liner may be fabricated and used in lieu of upper134 and lower118 liners. It is also to be appreciated that different sized upper134 and lower118 liners may be utilized and that the embodiments illustrated herein are used merely as an aid in describing the present invention. Theupper liner134 andlower liner118 will now be discussed in turn.
• Thechamber100 generally includes anannular sidewall106, abottom wall108, and alid assembly102 that define achamber volume110. Generally, thechamber volume110 is bifurcated into a process volume112 (the upper region of the chamber) and a pumping volume114 (the lower region of the chamber).
• Thebottom wall108 has a pumpingport138 through which excess process gases and volatile compounds produced during processing are exhausted from thechamber100 toexhaust system110 by avacuum pump109. Thebottom wall108 additionally has two apertures116 (only one of which is shown inFIG. 2) that provide access to thesecond liner118 from the exterior of thechamber100.
• Embodiments of thelid assembly102 are detailed in the plan views ofFIGS. 3A, 3B and cross-sectional view ofFIG. 4. In one embodiment illustrated inFIG. 4, thelid assembly102 comprises thefirst liner134 and alid202. Thefirst liner134 has an outwardly extendingflange342 that rests upon the top of thesidewall106. The various components oflid assembly102 are appropriately configured to provide a gas tight seal where needed to ensure the vacuum integrity of theprocessing volume112. For example,lid assembly102 may be generally biased downwardly when thelid202 is clamped in place, thelid assembly102 exerts a downward force upon thesecond liner118 when installed in theprocessing chamber100.
• Continuing withFIG. 4, thefirst liner134 is fabricated from a thermally conductive material, such as for example, anodized aluminum, stainless steel, ceramic or other compatible material. Thefirst liner134 can be easily removed for cleaning and provides a removable surface on which deposition can occur during processing. Thefirst liner134 comprises acenter section310 having a dish-shapedtop surface312, and abottom surface316. The dish-shapedtop surface312 has aperimeter314 that is connected to the outwardly extendingflange342. Extending from thebottom surface316 is acylindrical liner wall318. Thebottom surface316 andliner wall318 haveinterior surfaces320 that are exposed to theprocess volume112. As described in greater detail below in section IV, theinterior surfaces320 ofupper liner134, or optionally, any liner exposed toprocess volume112 may be textured to improve adhesion of deposited films by reducing surface tension in the film.
• Afluid passage322 is disposed withincenter section310. Thefluid passage322 may be formed by a number of conventional means such as, for example, forming thefluid passage322 during casting. Turning briefly toFIG. 3A, another method for formingfluid passage322 is by drilling a number of intersectingblind holes208 wherein eachhole208 is sealed by aplug210, thus forming thefluid passage322.
• Returning toFIG. 4, two bosses326 (only one of which is shown inFIG. 4) protrude from thesurface312 of thecenter section310. Eachboss326 has acenter hole328 that is fluidly coupled to thefluid passage322 via therespective bore324.
• Thefluid passage322 receives fluid from the heat exchanger orcoolant source121. Like all surfaces exposed to the plasma,first liner134 is heated by plasma processes conducted in the plasma etch chamber. The fluid regulates the temperature of thefirst liner134 by drawing heat conducted through thefirst liner134 into the fluid. As the fluid is circulated through thefirst liner134 from thefluid source121, the amount of heat removed form thefirst liner134 is controlled, thus permitting thefirst liner134 to be maintained at a predetermined temperature.
• The fluid, which may be liquid and/or gaseous fluids, is flowed through thefluid passage322 to provide temperature control to thefirst liner134. The fluid is preferably a liquid such as de-ionized water and/or ethylene glycol. Other fluids, such as liquid or gaseous nitrogen or freon, can also be used. Alternatively, thefirst liner134 could be uniformly heated using heated fluids.
• One skilled in the art will be able to devise alternate configurations for the fluid passage utilizing the teachings disclosed herein. For example, as depicted inFIG. 3B, alid assembly202 may comprise afirst fluid passage322A and asecond fluid passage322B. The first and secondfluid passages322A and B may share acommon inlet330iand a common outlet330oas illustrated inFIG. 3B. Optionally, additional inlets and outlets may be utilized. The first and secondfluid passages322A and322B double back in a “two tube pass” configuration. Additional tube passes may alternatively be incorporated.
• Returning toFIGS. 3A and 4, quick-connect fluid couplings are utilized to fluidly connect afluid supply121 and thefirst liner134 to facilitate the rapid removal and replacement of thefirst liner134 from thechamber100. Typically, a quick-connect330 having a male pipe thread-form is threaded into a female thread-form in thecenter hole328 of theboss326. Themating coupling332 is affixed to the terminal end of afluid supply line334. Thefluid supply line334 couples thepassage322 to thefluid supply121. One advantage of this configuration is that during the change out of thefirst liner134, thefluid supply line334 can be disconnected without the aid of tools. However, other means of coupling thefirst liner134 to the fluid supply line334 (for example, pipe threads, barbed nipples, collet connectors and the like) may also be used. Quick-connects are commercially available and are generally selected based on port size (thread-form and flow capacity) and the brand used in a particular wafer processing facility or fab (for maintenance inventory purposes).
• Returning toFIG. 4, theliner wall318 is sized to slip inside thesidewall106 with minimal clearance. Theliner wall318 may vary in height, and may, when used without a second liner, extend to thechamber bottom108. Generally, if both thefirst liner134 andsecond liner118 are utilized (as shown inFIG. 2), the liners are proportioned to fit inside thechamber100 to provide the compressive force necessary to seal thesecond liner118 to thechamber bottom108 when thelid assembly102 is clamped in place.
• Theliner wall318 may additionally contain a number of other ports for various purposes. An example of such other ports is a substrate access port to align with the slit opening of thechamber100.
• Returning toFIG. 2, thesecond liner118 will now be described. Thesecond liner118 is disposed in thechamber100 to surround thesubstrate support124 and form a deposition area that can be easily removed and cleaned.
• Thesecond liner118 has afluid passage119 in which fluid is provided from thefluid source121 by aconduit123. As with the operation of thefirst liner134, the fluid regulates the temperature of thesecond liner118 by drawing heat conducted through thesecond liner118 into the fluid. As the fluid is circulated through thesecond liner118 from thefluid source121, the amount of heat removed form thesecond liner118 is controlled, thus permitting thesecond liner118 to be maintained at a predetermined temperature.
• FIGS. 5 and 6 depict thesecond liner118 in greater detail. Thesecond liner118 is fabricated from a thermally conductive material, for example anodized aluminum, stainless steel, or other compatible material. Thesecond liner118 comprises abase section502 connecting aninner wall504 and anouter wall506. The interior surfaces508 of thebase section502,inner wall504 andouter wall506 are exposed to thepumping volume114. As described in greater detail below in section IV entitled “Chamber Surface Alterations to Improve Adhesion,” and with regard to the alternative embodiments illustrated inFIG. 8 andFIGS. 13-20, theinterior surfaces508 may be textured to increase improve adhesion of deposited films by reducing surface tension in the film.
• Thebase section502 contains afluid passage119. Thefluid passage119 may be formed by conventional means such as those described above with regard to thefirst liner134. In one embodiment, thefluid passage119 is substantially circular, beginning and ending adjacent to anexhaust port520 that is disposed through thesecond liner118.
• Each end of thefluid passage119 terminates in aboss510 that protrudes from an exterior surface of thebase502. Theboss510 interfaces with thebottom wall108 and ensures the proper orientation of thesecond liner118 in the chamber100 (i.e., all ports align). To facilitate the rapid change out of thesecond liner118, quick-connect fluid couplings are utilized between thesecond liner118 and aconduit123 that fluidly couples thepassage119 to thefluid source121.
• Theinner wall504 is generally cylindrical and is sized to slip over thesubstrate support124 with minimal clearance. Theinner wall504 optionally comprises a plasma containment means516. Plasma confinement means516 may be, for example, acontainment magnet516 disposed within aprotrusion518 formed withininner wall504 and facing theouter wall506. Theprotrusion518 is positioned away from the base on theinner wall504 so that theplasma containment magnet516 resides below thesubstrate support124 when thesecond liner118 is installed. Theplasma containment magnet516 may be asamarium magnet516. Alternative embodiments of the plasma confinement feature of the present invention are described in greater detail below in a section entitled Plasma Confinement. (FIGS.21 to27.)
• Theouter wall506 is generally cylindrical and is sized to define a minimal gap with thechamber walls106. Theouter wall506 may vary in height, particularly if afirst liner134 is also utilized as described above. Theouter wall506 additionally contains theexhaust port520 that aligns with the pumpingport138. Theexhaust port520 may partially encompass a portion of thebase wall108. Theexhaust port520 provides fluid access of gases in thepumping volume114 to thethrottle valve8 andvacuum pump109.
• Theouter wall506 may optionally include athrottling ridge522 extending into thepumping volume114. The throttlingridge522 is positioned proximate theprotrusion518 on theinner wall504 to create anannular flow orifice524 for controlling the flow of gases moving from theprocess volume112 to thepumping volume114. Theouter wall506 may additionally contain a number of other ports for various purposes. An example of such other ports is asubstrate access port526 that aligns with a slit opening139 in thesidewall106 to allow transfer ofsubstrate10 in and out of thechamber100. Turning briefly toFIG. 28 which illustrates another embodiment ofliner118,outer wall506 does not include athrottling ridge522 andonly protrusion518 extends into pumpingvolume114.
• The operation of a temperature controlled liner according to the present invention can be illustrated while viewingFIG. 2. In operation, the temperature of thefirst liner134 andsecond liner118 are controlled by flowing fluid through thepassages119 and322 within therespective liners118 and134, from thefluid source121. The fluid regulates the temperature of theliners118 and134 by transferring heat between theliners118 and134 and the fluid. The fluid from thefluid source121 is controlled in both temperature and rate of flow, thus controlling the amount of heat removed from theliners118 and134, and permitting theliners118 and134 to be maintained at a predetermined temperature. In an exemplary embodiment, a user provides a set point for liner wall temperature, for example, intocontroller140 andcontroller140 regulates the amount and temperature of fluid output byheat exchanger121 to maintain the user input setpoint.
• Because the temperature of theliners118 and134 is controlled predominantly by the fluid in thepassages119 and322 and less reliant upon conduction with thechamber walls106, theliners118 and134 are able to maintain a substantially uniform, controllable temperature during a variety of plasma etch process conditions, such as for example, increased RF powers and higher magnetic fields. Thus, by controlling the temperature of thechamber liner104, the amount of material deposited upon thechamber liner104 can be better controlled and the stresses within the deposited material can be minimized thereby improving adhesion of the deposited material. Because the temperature controlled liners enables improved adhesion of generated by-products, a wider variety of process gas compositions including deposit forming chemistries such as those encountered in oxide an dielectric etch process may be used with greater confidence. Process engineers have greater latitude in devising etch gas compositions because the byproducts formed by these gas compositions pose less of a contamination threat because of the improved adhesion capability of the liners of the present invention. In this way, the process window of etch chambers having embodiments of the present invention are expanded to include a wider variety of useable etch gas compositions.
• Thermally Differentiated Gas Supply System
• Returning toFIG. 4, an embodiment of the gas distribution system of the present invention will now be described. Thetop surface312 of thefirst liner134 comprises acenter depression336. Thecenter depression336 is covered by thelid202, defining aplenum338 at least partially between thelid202 and thecenter depression336. Thelid202 additionally has acentral hole340 that allows fluid flow from a passage344 in agas feedthrough212 fastened to thelid202. Thegas feedthrough212 is sealed to thelid202 to prevent gas leakage. Thegas feedthrough212 is generally coupled to fluid passages within thesidewall106 as to allow temperature conditioning of gases being delivered to theplenum338 from the gas source (not shown). Alternatively, thegas feedthrough212 may be directly coupled to the gas source.
• In one embodiment, the plurality ofapertures348 is disposed at least partially in thecenter depression336. Theapertures348 are generally positioned in a polar array about the center of thefirst liner134, although other positional locations may be utilized. Eachaperture348 is fitted with anozzle350a.Thenozzles350afacilitate distribution of process and other gases from within theplenum338 to theprocess volume112 of thechamber100. Thenozzle350ais generally fabricated from a non-conductive material, such as quartz, silicon carbide, silicon, aluminum nitride, aluminum oxide, Y2O3, Boron Carbide, or other materials such as sapphire.
• FIGS. 7a-7fdepict various alternative embodiments of thenozzle350athat advantageously minimize recirculative gas flows within the chamber. Whilereference numbers350 and350aare used, it is to be appreciated thatalternative nozzles350bto350fmay be used. Turning now toFIG. 7A. In one embodiment of the nozzle illustrated inFIG. 7A, thenozzle350aincludes a mountingportion717 and agas delivery portion715 that is in communication with thechamber volume110. The mountingportion717 has aflange710 extending from the perimeter of thenozzle350atypically towards the side of thenozzle350aexposed to theplenum338. Thenozzle350aadditionally comprises acentral passage724 that fluidly couples theplenum338 to thechamber volume110. Thecentral passage724 generally is positioned co-axially to the centerline of thenozzle350a.Optionally, additional passages may be utilized to fluidly couple theplenum338 and thechamber volume110. Additionally, the gas delivery portion of a nozzle may be flush with thefirst liner134 as illustrated, for example, innozzle350aofFIG. 7A andnozzle350bofFIG. 7B. Alternatively, the gas delivery portion of a nozzle may extend beyond thefirst liner134 as illustrated, for example, innozzle350cofFIG. 7C, in nozzle350dofFIG. 7D, innozzle350eofFIG. 7E, and innozzle350fofFIG. 7F.
• Returning toFIG. 7A, theflange710 mates with arecess712 disposed in thefirst liner134. Generally, acontact surface702 of theflange710 and amating surface704 of therecess712 have a surface finish having a flatness of about 1 mil or less which provides minimal gas leakage between thecontact surface702 and themating surface704. A exposedsurface716 of thegas delivery portion715 may have a smooth or textured surface.
• FIG. 7B illustrates another embodiment of a nozzle, anozzle350b,that is substantially similar tonozzle350awith the exception thatcentral passage724 is optional. Thenozzle350bhas a one ormore passages714 that provide fluid communication of theplenum338 with thechamber volume110. Generally, thepassages714 are at an angle to the centerline of thenozzle350b.Optionally, the mountingportion717 may extend into theplenum338.
• FIG. 7C illustrates another embodiment of a nozzle, anozzle350c,that comprises the mountingportion717 and thegas delivery portion735. The gas delivery portion has anend728 proximate the mountingportion717 and an opposing,distal end718 that protrudes into thechamber volume110. Theproximate end728 is generally coplanar or tangent to a surface of thefirst liner134 exposed to thechamber volume110. Thegas delivery portion735 may have a smooth or textured surface finish. Acentral passage720 extend at least partially through thenozzle350cfrom aside722 of the mountingportion717 exposed to theplenum338. One or moresecondary passages726 fluidly couple thecentral feed720 and thechamber volume110.
• Generally, anoutlet727 of each of thesecondary passages726 on the exterior of thegas delivery portion735 are positioned at least a distance “DIST” from theend728 of thegas delivery portion735. Additionally, thesecondary passages726 are orientated at anangle0 relative to theproximate end728. In one embodiment, DIST is greater than about 0.25 inches and θ ranges between about 15 and about 35 degrees.
• FIG. 7D illustrates another embodiment of the nozzle, nozzle350d,that is similar to thenozzle350c.The nozzle350d,however, additionally comprises acentral passage724 that extends along the centerline of thenozzle350c,communicating theplenum338 directly with thechamber volume110.
• FIG. 7E illustrates another embodiment of a nozzle, anozzle350e,that is similar to the nozzle350d.Thenozzle350e,however, only provides thecentral passage724 between theplenum338 and thechamber volume110.
• FIG. 7F illustrates another embodiment of the nozzle, anozzle350f,that is similar to thenozzle350c.Thenozzle350f,however, has a mountingportion717 and agas delivery portion732 that is at an oblique orientation to the mountingportion717. Thenozzles350a-350fhave been found to run cleaner (i.e., with reduced processing byproduct buildup) than conventional nozzles due to the proximity to the plasma thereby making the nozzles hotter and discouraging deposition of reaction by-products. Because the gas delivery configuration of the nozzles minimizes flow recirculation within the chamber, the amount of reaction by-products drawn towards the upper regions (i.e., the lid area) of the chamber are reduced.
• Common to the nozzles described above is that they have low thermal mass and are not provided with cooling mechanism. Consequently, they heat up during processing to a temperature above that of the cooled lid and liners, so as to thermally differentiate the nozzles from the lid and liners. This helps to dramatically reduce polymer deposition on the nozzles. Optionally, in order to ensure that any polymer that does get deposited on the nozzles, they are provided with surface roughness by bid blasting or by a chemical process.
• Additional alternative embodiments of the gas distribution system are illustrated inFIGS. 8-13. InFIGS. 8-13, in lieu ofnozzles350,mini-gas distribution plates220 having plural gas injection holes225 are provided incenter section310 ofliner134 tofluidly couple plenum338 and thechamber volume110. Likenozzles350, the area of each of themini-gas distribution plates220 facing the plasma is limited so that: (1) the area is contained within a region in which the turbulence from the injected gas in the vicinity of the inlets prevents or impedes polymer accumulation, and (2) the size or thermal mass of the mini-gas distribution plate is sufficiently low to allow rapid plasma-heating of the plate. In order to enhance the gas turbulence across the area of themini-gas distribution plate220, the gas injection holes225 in eachmini-gas distribution plate220 are angled relative to the surface of the plate facing the chamber interior. Preferably, the gas injection holes are angled so that the gas injection streams from adjacent holes cross one another or together form a vortex pattern. In an alternative embodiment of the placement of themini-gas distribution plates220, themini-gas distribution plates220 extend slightly out fromtop liner surface316 to enhance plasma-heating thereof and to enhance gas injection turbulence. Preferably, themini-gas distribution plates220 are each a relatively small fraction of the area of theentire ceiling316.
• Eachmini-gas distribution plate220 is formed of a semi-metal such as silicon or a dielectric such as silicon dioxide (quartz) or sapphire, or, alternatively, of a non-conductive material or of a material compatible with processes conducted withinprocessing chamber100. Eachmini-gas distribution plate220 hasplural gas inlets225 through which process gas is sprayed into the reactor chamber interior. Preferably, themini-gas distribution plates220 are thermally insulated from the temperature controlledliner134, so that they are readily heated by the plasma within the chamber. Eachgas distribution plate220 is sufficiently small relative to the ceiling—has a sufficiently small thermal mass—so as to be rapidly heated by the plasma upon plasma ignition. (For example, thefirst liner134 may have a diameter in a range of 9 inches to 14 inches, while agas distribution plate220 has an exposed diameter on the order of about 0.25-0.5 inch. As a result, the plasma heats eachmini-gas distribution plate220 to a sufficiently high temperature to prevent any accumulation of polymer thereon. The advantage is that thegas inlets225 of eachmini-gas distribution plate220, like the inlets ofnozzles350, can be kept clear of polymer.
• Preferably, the diameter of eachmini-gas distribution plate220 is sufficiently small so that the entirebottom surface220aof thegas distribution plate220 is enveloped within a region of gas flow turbulence of the process gas spray from theinlets225. Thus, for example, eachmini-gas distribution plate220 has an exposed diameter on the order of about 0.25-0.5 inch. This region has sufficient gas turbulence to retard or prevent the accumulation of polymer on thesurface220a.
• Referring toFIGS. 9 and 10, the gas turbulence around thebottom surface220ais enhanced by introducing a crossing pattern of gas spray paths from theplural gas inlets225 of themini-gas distribution plate220. The embodiment ofFIGS. 9 and 10 provides a vortex pattern (indicated by the arrows ofFIG. 9). This is accomplished by drilling each of thegas inlets225 at an angle A (as illustrated inFIG. 10) relative to theoutlet surface220aof themini-gas distribution plate220. Preferably, the angle A is in the range of about 20 degrees to 30 degrees. In an alternative embodiment illustrated inFIG. 11, the gas spray paths of theplural gas inlets225 are directed at other inlets in order to enhance the gas turbulence. This alternative spray pattern is illustrated by the arrows inFIG. 11.
• As a further aid in inhibiting the accumulation of polymer on themini-gas distribution plates220, theoutlet surface220aof theplate220 extends slightly below the surface of theceiling210 by a distance d, as shown inFIG. 12. The distance d is preferably about 0.02 inch to 0.03 inch or a fraction of the thickness of thegas distribution plate220. The enlarged cross-sectional view ofFIG. 12 illustrates one exemplary implementation in which thegas inlets225 are angled holes passing entirely through themini-gas distribution plate220. Process gas is supplied to thegas inlets225 by acommon manifold230 formed in theceiling316. Awater jacket240 of the water-cooledceiling316 is also shown in the drawing ofFIG. 12. Preferably, athermal insulation layer250, which may be aluminum nitride for example, is trapped between themini-gas distribution plate220 and theceiling316.
• In an embodiment where controlled polymer accumulation is desired such as an oxide etch process for example, thefirst liner134 is maintained at a sufficiently low temperature so that polymer accumulates on the exposed surfaces of thefirst liner134 as a very hard film which is virtually immune from flaking or contributing contamination to the chamber interior. The thermally differentiatedmini-gas distribution plates220 andnozzles350 are heated by the plasma to a sufficiently high temperature to inhibit accumulation of polymer thereon. Thus, thegas inlets225 are kept clear of any polymer. The small size of themini-gas distribution plates220 andnozzles350 enables the plasma to efficiently heat them to a temperature above a polymer deposition temperature. The small size also permits the concentration of gas inlets over thesmall surface220ato provide sufficient gas turbulence to further inhibit the accumulation of polymer on thesurface220a,inlets225, ornozzles350. The gas turbulence is enhanced by providing a crossed or vortex pattern of gas spray paths from each of thegas inlets225 of themini-gas distribution plate220, and having theoutlet surface220abelow theceiling316.
• Another advantage of the minimized size nozzle is that because the nozzles size is small relative to the temperature controlled lid, plasma formed in the processing volume will likely contact the temperature controlled lid surface thereby improving byproduct adhesion to the lid as described above. The combination of all of the foregoing features prevents any observable accumulation of polymer on any portion themini-gas distribution plate220 or the various nozzle embodiments.
• FIG. 8 illustrates an embodiment where there are fourmini-gas distribution plates220 mounted on thefirst liner134 at four symmetrically spaced locations overlying the periphery of thewafer10.FIG. 8 also illustrates a plurality of semi-spherical bumps formed on the surface of the ceiling. These bumps are about 0.5 to about 1.5 mm high and are spaced about 1 mm apart.Bumps300 are yet another alternative embodiment of the chamber surface texturing described in more detail below in the next section entitled “Chamber Surface Alterations to Improve Adhesion”. Of course, additionalmini-gas distribution plates220 ornozzles350 may be provided in other embodiments, or their placement modified from the arrangement illustrated inFIG. 4 and8.
• Chamber Surface Alterations to Improve Adhesion
• Another advantage of the present invention is the use of chamber surface topography to improve the adhesion of by products deposited on chamber surfaces. For example, in a conventional fluorocarbon based plasma etch of oxide features, polymeric byproduct formation is common. Referring toFIG. 2, for example, by-product deposition would occur on the surfaces of the twoliners118,134 andlid102 exposed to theplasma148. After the deposits accumulate to a certain thickness, the deposits will begin to flake off the lid and the chamber liners, thereby contaminating the semiconductor devices being fabricated.
• It is believed this aspect of the present invention further improves adhesion of reaction byproducts or other material deposited on surfaces within the process chamber that are exposed to process gases, thereby allowing the chamber to be operated for longer time intervals between cleaning such surfaces. Moreover, the improved byproduct adhesion capability promotes the use of expanded process gas compositions—including those with high rates of byproduct formation. Specifically, chamber interior surfaces such as the surface of the temperature controlled liner and lid, are fabricated with a surface contour or “texture” having topographical features—i.e., alternating protrusions and depressions (peaks and troughs)—whose width, spacing, and height dimensions are between 100 microns (0.1 mm) and 100 mm, and preferably in the range of 500 microns (0.5 mm) to 8000 microns (8 mm). In contrast, the average roughness of surfaces treated by conventional bead blasting is about 4 to 6 microns (0.15 to 0.23 mil), which is at least16 times smaller than the features of the invention.
• By “topographical feature” or “elevation feature” of the surface we mean an area whose elevation deviates from the average surface elevation. A topographical feature can be either a convex protrusion or a concave depression. The “height” of a feature is the peak-to-trough deviation in elevation. If the feature is a concave depression, the “height” of the feature is the depth of the depression.
• It is believed that our textured surface improves adhesion of the deposited material for at least two reasons. One reason is that vertical contours (contours perpendicular to the average surface plane) increase compressive forces within the deposited film in a direction normal to the surface, thereby resisting cracking of the film due to thermal expansion and contraction. A second reason is that a textured surface has a greater surface area for the material to bond to than a flat surface.
• The surface area increases in proportion to the depth of the depressions or the height of the protrusions. While increasing the height dimension in order to increase the surface area by improves adhesion of deposited material, increasing the height beyond a certain value can become disadvantageous. First, an excessive height dimension can make the textured surface harder to clean. Secondly, if the textured surface is a thin, removable chamber lid or liner rather than a comparatively thick chamber wall, an excessive height dimension can reduce the strength and rigidity of the lid or liner, making it more susceptible to accidental damage.
• The texturing of our invention can be applied to the surface of any component of the process chamber. (By “component” we mean any object in or on the chamber.) The texturing preferably should be applied to any large surface that is exposed to the process gases in the chamber interior and that is either above or near the wafer. The chamber surfaces for which it is most important to provide the texture of the invention typically are the lower surface of the chamber roof (i.e., interior surfaces of the chamber lid102) and theliners134 and118. Since the chamber roof is directly above the wafer being processed, any particles that flake off of the roof probably will fall on the wafer, thereby causing a defect in the wafer. Since the chamber side wall or lining is very close to the perimeter of the wafer, there also is a high risk that particles flaking off the side wall or lining will fall on the wafer. It is much less important to provide textured surfaces on chamber components positioned below the wafer, since particles flaking off of such surfaces are unlikely to deposit on the wafer.
• Different shapes and dimensions of depressions and protrusions in the exposed surfaces of the chamber roof and side wall lining were tested. All shapes tested greatly improved adhesion of deposited material compared with either smooth, untreated surfaces or surfaces roughened by bead blasting.
• Viewed in conjunction withFIG. 4,FIGS. 13 and 14 are top and sectional views, respectively, of a portion of thelower surface316 of aliner134 having atexture60 consisting of a 2-dimensional array ofsquare protrusions60. For clarity,apertures348 andnozzles350 have been omitted. The protrusions have height H, width W, and spacing S between adjacent protrusions.FIG. 15 shows atexture60ain which the topographical features are square depressions into the surface rather than protrusions, and in which the sides of the square depressions are formed at an oblique angle θ relative to the horizontal surface between the depressions, so that each depression is shaped as an inverted 4-sided pyramid with a flat bottom rather than a sharp apex.FIGS. 16 and 17 are top and sectional views of analternative texture1605 in which the depressions are rounded or hemispherical in shape.
• FIGS. 18 and 19 are perspective and sectional views, respectively, of a texture consisting of a plurality ofcircumferential grooves1805 in aliner118.
• FIG. 20 is a perspective view of aliner118 having both circumferential1805 and longitudinal1810 grooves.
• While each topographical feature has been characterized as either a protrusion or a depression, it is equivalent to consider the area between the depressions to be protrusions on the surface. In other words, it is arbitrary whether the protrusions or the depressions are designated as the topographical features. Therefore, referring for example toFIG. 17, the spacing S between depressions or protrusions preferably should be the same order of magnitude as the width W. More preferably, the spacing S and width W should differ by a factor of 2 or less. Similarly, the height H preferably should be the same order of magnitude as the width W and spacing S, and more preferably should be within a factor of 2 of those other two dimensions.
• In any of the embodiments, we expect the adhesion of the deposited film to the textured surface will maximized if there are no sharp corners in the textured surfaces of the chamber components, because sharp corners generally increase stress in the film. Consequently, the edges of the topographical features should have rounded corners, with as high a radius of curvature as practical. Preferably, the radius of curvature ranges from between 130 microns (0.13 mm) to about 500 microns (0.5 mm).
• Test Results—Control
• We tested the invention by using a plasma etch chamber to perform a plasma process for etching films of silicon dioxide on silicon wafers, using a conventional fluorocarbon etchant gas mixture including C₄F₈and CO. For the control, the process chamber had an aluminum nitride ceramic roof and an anodized aluminum side wall liner, both of which were smooth (i.e., had no surface texture treatments to improve adhesion.)
• The etching process produces fluorocarbon reaction products which form polymer films on exposed inner surfaces of the chamber roof and side walls. We found that, with conventional smooth roof and side wall liner, the polymer deposited on these surfaces began flaking off after the polymer film reached a thickness of 0.6 to 0.65 mm. The thickness at which flaking occurred was independent of changes in process parameters.
EXAMPLE 1Pyramid Depressions in Aluminum Nitride Roof
• We fabricated a chamber roof (gas distribution plate) as a circular disk of aluminum nitride ceramic, 0.5 inch (13 mm) thick, in which we divided the lower circular surface of the roof (the surface exposed to the chamber interior) into four quadrants, with four different surface textures fabricated in the four quadrants. The first quadrant was smooth, and the second quadrant was bead blasted with silicon carbide particles.
• The third and fourth quadrants both had thepyramid texture60ashown inFIG. 15, with bead blasting subsequently applied to the fourth quadrant but not the third. The dimensions of the pyramid features were: angle θ=45°, height H=0.6 mm, width W=1.5 mm, spacing S=0.6 mm. We calculate that the third quadrant had asurface area 30% greater than that of the first quadrant due to its pyramid texture.

  TABLE 1
  Example 1

  Quadrant	Pyramid Texture	Bead Blasting
  1	No	No
  2	No	Yes
  3	Yes	No
  4	Yes	Yes

• We expect that a pattern of square depressions orprotrusions60 as shown inFIG. 14 would be preferable to the pyramid-shaped depressions actually tested, because the square features have a greater surface area. As stated earlier, we expect that maximizing the surface area of the surface contour is advantageous in order to maximize the adhesion of the material deposited thereon.
• We installed the roof in a conventional plasma etch chamber and performed the same plasma etch process performed in the Control. We found that the third quadrant of the roof exhibited the best polymer adhesion. Compared to the smooth first quadrant, we were able to process 2.5 times more wafers before material deposited on the third quadrant began flaking. At this point, the polymer layer deposited on the third quadrant had a thickness of 1.2 mm, which is 85% thicker than the maximum polymer thickness that could be deposited on a conventional smooth or bead blasted surface without flaking.
• Because bead blasting conventionally had been used to improve adhesion of deposited material, we were surprised to observe that bead blasting the pyramid textured surface was detrimental to adhesion. Specifically, when we halted the test after depositing 1.2 mm of polymer on the lid, we observed a small amount of flaking from the fourth quadrant, and no flaking whatsoever from the third quadrant. We surmise that the bead blasting created sharp corners in the surface of the roof that increased stress in the polymer film, thereby promoting cracks in the film.
EXAMPLE 2Different Pyramid Dimensions in Aluminum Nitride Roof
• A second aluminum nitride roof (gas distribution plate) was fabricated as described for Example 1. The four quadrants were textured with pyramids having different dimensions, as summarized in Table 1. In the first quadrant, the pyramid dimensions were identical to those ofquadrant 3 of Example 1. In the other three quadrants, the height H of the pyramid depressions was increased to 1.1 mm. Inquadrants 3 and 4, the angle θ of the pyramid walls relative to the horizontal surface was decreased to 30°. Inquadrants 2 and 4, the width W and spacing S were increased to 2.5 mm and 1.0 mm, respectively. All four quadrants exhibited no flaking of the polymer deposits.

  TABLE 2
  Example 2

  Quadrant	Angle θ	Height H	Width W	Spacing S
  1	45°	0.6 mm	1.5 mm	0.6mm
  2	45°	1.1 mm	2.5 mm	1.0mm
  3	30°	1.1 mm	1.5 mm	0.6 mm
  4	30°	1.1 mm	2.5 mm	1.0 mm

EXAMPLE 3Hemispherical Depressions in Aluminum Oxide Roof
• We fabricated a roof of a 0.5 inch (13 mm) thick plate of aluminum oxide (alumina) ceramic. Alumina has a much lower thermal conductivity than aluminum nitride, but it has the advantage of being readily machinable. We created the pattern of depressions shown inFIGS. 16 and 17 by drilling in the alumina an array of approximately hemispherical holes, or holes having an arcuate cross section, having a hole diameter W of 4 mm and a spacing S between the perimeters of adjacent holes of 1 mm. We tested two prototypes in which the depth of the holes (the topographical feature height H) were 1 mm and 2 mm, respectively. Both prototypes exhibited no flaking of the polymer deposits.
EXAMPLE 4Square Protrusions in Anodized Aluminum
• FIGS. 13 and 14 show an aluminum roof in which we machined an array of square protrusions. While the section is illustrated as solid the same features or protrusions may be incorporated into thetop ceiling316 having a plurality ofgas inlets350 ormini-gas distribution plates220. The aluminum was anodized after the machining. In one prototype the protrusions had 1 mm width W, 1.5 mm height H, and 3 mm spacing S. In a second prototype, the protrusions had 2 mm width W, 2 mm height H, and 5 mm spacing S. Both prototypes exhibited no flaking of the polymer deposits.
• In the second prototype, we also tested an implementation of the gas inlet holes in the gas distribution plate. Instead of a conventional array of gas inlet holes uniformly distributed over the surface of the plate, we installed in the plate only eleven quartz discs (not shown), where each quartz disc was 10 mm diameter and included eleven gas inlet holes 0.6 mm diameter.
EXAMPLE 5Grooves in Anodized Aluminum
• FIGS. 18 and 19 are perspective and sectional views, respectively, of a cylindricalside wall liner118 composed of anodized aluminum in which we machined a series ofcircumferential grooves1805 using a lathe. Each groove had 1 mm width and 1 mm depth, and adjacent grooves were spaced apart along the axis of the cylindrical liner by 3 mm. The aluminum was anodized after the machining.
• FIG. 20 is a perspective view of a similar cylindrical liner having both circumferential1805 and longitudinal1810 grooves of the same width, depth, and spacing dimensions stated in the preceding paragraph.
• Both prototypes exhibited no flaking of the polymer deposits. However, theFIG. 20 embodiment is expected to provide superior adhesion because its surface area is greater than that of the embodiments illustrated inFIGS. 18 and 19.
• An advantage of the embodiments ofFIGS. 18, 19 and20 is that machining grooves in aluminum typically is less expensive than the other fabrication methods described earlier.
• While the different textures may be illustrated and described with regard tofirst liner134 orsecond liner118, it is to be appreciated that the textures described herein may be applied to either or bothliners134,118. In alternative embodiments,liner134 may have a different surface treatment thanliner118. In one specific embodiment,liner134 may havetexture1605 whileliner118 hascircumferential groove texture1805.
• Plasma Confinement
• Another aspect of the byproduct management feature of the present invention is the use of a plasma confinement system to contain the plasma in theprocessing region112. Containing the plasma within theprocessing region112 helps prevent byproduct accumulation in thepumping volume114. Reducing or eliminating byproduct accumulation in pumpingvolume114 reduces the likelihood that byproduct deposition will occur in and potentiallydamage pump109. The plasma confinement feature of the present invention may be better appreciated through reference toFIG. 21.
• FIG. 21 is an enlarged partial view of the etchedchamber100 ofFIG. 1.Lid102 has been removed for clarity. Avacuum pump109 exhausts gases from theprocessing volume112 through annular exhaust manifold andcylindrical pumping channel138 so as to reduce the total gas pressure in the chamber to a level suitable for the plasma process intended to be performed in the chamber. Athrottle valve8 is mounted within thepumping volume114. Thethrottle valve8 regulates the gas pressure within the chamber by controlling the impedance to gas flow within the pumpingchannel138, thereby controlling the pressure drop across the pumping channel as required to maintain the desired chamber pressure.
• While described as separate liners, it is to be appreciated thatliners36 and38 could be combined into a single liner such as described above with regard toliner118. It is to be appreciated that each of the plasma confinement features described herein with regard toliners36, and38 apply toliner118. It is to be further appreciated thatliners36 and38 are equipped with internal conduits such asconduit119 ofliner118 for circulating temperature controlled fluid as described above with regard toFIG. 6 andliners118 and143.
• Theinner liner38 and the lower half of theouter liner36 respectively function as the inner and outer walls of theannular exhaust volume114. Theannular flange40 at the bottom of theinner liner38 includes anarcuate aperture42, aligned with thecylindrical pumping channel138, to permit exhaust gases to flow from the annular exhaust manifold, through theflange aperture42, and then through thecylindrical pumping port138 to thethrottle valve8 and thepump109.
• The exhaust channel of the illustrated chamber includes an annular exhaust manifold and a cylindrical pumping channel. The annular exhaust manifold is coaxial with the chamber interior and extends around all or most of the azimuth of the chamber interior. The cylindrical pumping channel is coupled to the exhaust manifold at one azimuthal position. Some conventional plasma chambers include an annular exhaust manifold coupled directly to the exhaust pump without any intermediate pumping channel. Other conventional plasma chambers couple the pump to the chamber interior using only a pumping channel that does not extend around the azimuth of the chamber interior. In this patent specification, the term “exhaust channel” or “exhaust passage” encompasses either an annular exhaust manifold or a pumping channel, or the two in combination.
• Exhaust Channel and Magnet for Confining Plasma
• An exemplary embodiment of the invention, shown inFIGS. 21-23, employs two features—agas flow deflector522,516 and amagnet system50—that operate synergistically to prevent the plasma body within the chamber interior from reaching the exhaust pump. In addition to its beneficial functions as detailed below, this arrangement assists in providing high pumping capacity while avoiding polymer deposition in the pumping system. That is, as explained in the present disclosure, one feature of the inventive chamber is the high flow pumping capability for reduced residence time of the gas molecules. However, for maintenance reasons, it is advisable to constrain or limit the plasma from reaching to the pumping area of the chamber. The arrangement described below assists in achieving this goal.
• Specifically, the interior of theexhaust manifold30 includes at least onedeflector522,516 that deflects at least a substantial portion of the exhaust gases transversely, instead of allowing all of the exhaust gases to flow in an unobstructed straight path through the exhaust manifold. (By “transversely” we mean perpendicular to the direction of the path along which the gases would flow in the absence of the deflector.)
• The deflector creates turbulence in the flow of exhaust gases that increases the rate of collisions of reactive species in the gases with the deflector and with the walls of the exhaust manifold near the deflector. The collisions promote surface reactions among the reactive species so as to produce deposits on the walls. This depletes the exhaust gases of the reactive species that tend to produce such deposits, thereby greatly reducing or eliminating the concentration of such reactive species in the exhaust gases downstream of the deflector, and therefore greatly reducing or eliminating undesirable deposits on thethrottle valve8 and pump109.
• The deflector also increases the rate of collisions of charged particles in the exhaust gases so as to promote recombination of such charged particles, thereby reducing the concentration of charged particles in the exhaust gases.
• Additionally, a magnet system50 (52-57) is positioned near thedeflector522,516 so as to produce a magnetic field within the exhaust manifold near the deflector. The magnetic field preferably has a substantial component directed transverse to the direction of exhaust gas flow through the manifold. The transverse component of the magnetic field transversely deflects moving electrons so that they are more likely to recombine with positive ions, thereby reducing the concentration of charged particles in the exhaust gases.
• Since the deflector and the magnetic system both reduce the concentration of charged particles in the exhaust gases, the two in combination can reduce the concentration sufficiently to extinguish the plasma downstream of the deflector and magnet system. Specifically, the magnetic field should be strong enough, and the turbulence caused by the one or more deflectors should be great enough, so that the combined effects of the magnetic field and the deflector prevent the plasma body within the chamber from reaching thethrottle valve8 andexhaust pump109.
• The plasma confinement effect of the magnetic field permits the use of a wider and/or less sinuous exhaust channel than would be required to block the plasma without the magnetic field. Therefore, the pressure drop across the exhaust channel can be reduced in comparison with prior art designs that rely entirely on the sinuousness of the exhaust manifold to block the plasma.
• In the embodiment shown inFIGS. 21-23, the deflector consists of two coaxial,annular protrusions522,516 extending into the gas passageway of theexhaust manifold30 from the walls of the manifold. Theupper protrusion522 extends radially inward from theouter liner36, and thelower protrusion516 extends radially outward from the inner liner orcathode shield38. Because the two protrusions overlap each other radially, they do not permit any of the exhaust gases to travel in a straight line through the exhaust manifold, thereby maximizing the likelihood that reactive species in the exhaust gases will collide with either the protrusions or the walls of the exhaust manifold.
• We define a “magnet system” as one or more magnets in combination with zero, one or more magnetically permeable pole pieces to form a magnetic circuit having a north pole and a south pole. In the embodiment ofFIGS. 21-23, themagnet system50 consists of twoannular magnets52,53 mounted coaxially with theannular exhaust manifold30 and spaced apart along the axis of the manifold. The two annular magnets are identical, except that thefirst magnet52 has its north and south poles at its radially inner and outer ends, respectively, whereas thesecond magnet53 has its north and south poles at its radially outer and inner ends, respectively. Themagnet system50 also includes a cylindrical, magneticallypermeable pole piece54 mounted coaxially with the twomagnets52,53 so as to abut and extend between the radially inner ends of the two magnets, thereby completing a magnetic path or “magnetic circuit” between the two magnets.
• Consequently, thenorth pole56 of themagnet system50 is the north pole of the firstannular magnet52, i.e., the pole of the first magnet opposite the pole that abuts thepole piece54. Thesouth pole57 of themagnet system50 is the south pole of the secondannular magnet53, i.e., the pole of the second magnet opposite the pole that abuts thepole piece54.
• Themagnet system50 preferably is mounted within thelower protrusion516 so that the ends of the north andsouth poles56,57 of the magnet system are as close as possible to the narrow portion of the gas passageway within the exhaust manifold that is radially outward of the protrusion. Mounting the magnet system close to the narrowest portion of the exhaust manifold passageway is desirable to maximize the magnetic field strength to which the exhaust gases are subjected.
• An exemplary implementation of the magnet system just described has a U-shaped cross section as shown inFIGS. 21-23, with the base of the “U” pointing radially inward and the open end of the “U” pointing radially outward. More specifically, the shape of the magnet system is that of a U-shaped horseshoe magnet that is revolved around the longitudinal axis of the chamber.
• The magnetic field pattern produced by this U-shaped magnet system, represented byfield line58 inFIG. 22, is desirable because it is concentrated primarily within the passageway of the exhaust manifold. This concentration has at least two advantages. One advantage is that, as stated above, it maximizes the magnetic field strength to which the exhaust gases are subjected, thereby maximizing the effectiveness of the magnet in extinguishing the plasma downstream of the magnet.
• A second advantage of the U-shaped magnet system is that the magnetic field strength declines rapidly along the longitudinal axis of the chamber, so that the magnetic field strength is low at theworkpiece10. To minimize the risk of damaging the workpiece by ion bombardment or electrostatic charge accumulation, the magnetic field strength at theworkpiece10 should be as low as possible, preferably no greater than 5 gauss, and more preferably no greater than 3 gauss. The magnet system is mounted in thelower protrusion516 rather than theupper protrusion522 in order to position the magnet system as far as possible from theworkpiece10, thereby minimizing the strength of the magnetic field at theworkpiece10.
• FIG. 24 shows analternative magnet system60 whose magnets and pole pieces are interchanged relative to the embodiment ofFIGS. 21-23. Specifically, the upper and lowerannular members62,63 are magnetically permeable pole pieces rather than magnets. Thecylindrical member64 is a magnet rather than a pole piece, the cylindrical magnet having a north magnetic pole at the upper end of its longitudinal axis abutting theupper pole piece62 and a south magnetic pole at the lower end of its axis abutting thelower pole piece63.
• A possible alternative implementation of the exhaust manifold could omit theupper protrusion522, relying on the combination of thelower protrusion516 and themagnet system50 to block the plasma.
• Another alternative exhaust manifold design would omit the lower protrusion516 (which extends radially outward from the inner liner38) and substitute a modifiedmagnet system51, shown inFIG. 25, that is mounted within the upper protrusion522 (which extends radially inward from the outer liner36). The north and southmagnetic poles56,57 of the modifiedmagnet system51 should be adjacent the gas passageway at the radially inner end of the protrusion44. This can be accomplished using thesame magnets52,53 andpole piece54 as in theFIG. 23 magnet system, but with thepole piece54 moved from the radially inner end to the radially outer end of the two magnets, as shown inFIG. 25.
• FIG. 26 shows analternative magnet system61 that differs from theFIG. 25magnet system51 in that the magnets and pole pieces are interchanged. (See the discussion of theFIG. 24 embodiment above.)
• We also tested the exhaust manifold design shown inFIG. 27 in a plasma chamber that otherwise was identical to the chamber shown inFIG. 21. The exhaust manifold ofFIG. 27 includes upper and lowerannular magnets68,69 mounted within the upper andlower protrusions522,516, respectively, of theexhaust channel30. Theupper magnet68 has north and south poles at its radially inner and outer ends, respectively. Thelower magnet69 has north and south poles at its radially outer and inner ends, respectively. Consequently, the north and south poles of the upper magnet are aligned with the south and north poles of the lower magnet. The resulting magnetic field, depicted bymagnetic field lines70, is highly concentrated in the region of the exhaust manifold channel or passageway between the two protrusions. As explained in the preceding discussion of theFIG. 21 embodiment, such concentration is desirable to maximize the strength of the magnetic field to which the exhaust gases are subjected and to minimize the magnetic field at theworkpiece10.
• To facilitate testing theFIG. 27 embodiment with different gaps between upper andlower protrusions522,516, our prototype included anannular dielectric spacer72 below theouter dielectric liner36. By substituting athicker spacer72, we could increase the height of theupper protrusion522 and thereby increase the gap between the two protrusions. We used thesame magnets68,69 for every spacer thickness we tested. Therefore, when we substituted a thicker spacer, we both increased the gap and decreased the magnetic field strength in the gap.
• In these tests we found that the plasma was successfully blocked from extending below the lower protrusion when the gap between the upper and lower protrusion was 0.5 inch or less and the magnetic field strength in the gap was at least 100 or 150 gauss. We also found that, in the illustrated chamber, the magnetic field strength declined fast enough away from the magnets so that the magnetic field strength at theworkpiece10 was less than 3 gauss, which we consider low enough to avoid risk of damage to the workpiece. However, when we tested a wider gap between the two protrusions, and therefore a lower magnetic field strength in the gap, we found that the plasma was not successfully blocked.
• We currently prefer theFIG. 21 embodiment because more manufacturing labor is required to mount magnets within two protrusions as in theFIG. 27 design in comparison with mounting magnets in only one protrusion as in theFIG. 21 design.
• Another alternative embodiment of the exhaust manifold would be to omit one protrusion and its corresponding magnet from theFIG. 27 embodiment. We tested a prototype that was identical to the one shown inFIG. 27, except that theupper protrusion522 and theupper magnet68 was omitted leaving only the lower protrusion and magnet as illustrated inFIG. 28. While this prototype successfully, blocked the plasma from extending below the lower protrusion, we considered the magnetic field at the workpiece to be undesirably strong. However, this embodiment might be suitable for use in semiconductor fabrication processes in which the workpiece is not overly susceptible to damage by ion bombardment or electrostatic charge accumulation.
• More generally, thedeflector522,516 need not be one or more protrusions extending from the walls of the exhaust channel, but can be any structure within the exhaust channel that causes substantial turbulence in the exhaust gases. As described earlier, such turbulence will promote recombination of charged particles so as to help extinguish the plasma downstream of the turbulence, and it will promote surface reactions among reactive species so that reaction products will be deposited on surfaces near the deflector rather than on pumpingcomponents8,109 downstream.
• The deflector and magnet system can be mounted in any part of the exhaust channel, such as the pumping channel32, even though they are mounted in the annular exhaust manifold in the preferred embodiment.
• Of course, any materials between the magnet system and the interior of the exhaust channel should be non-magnetic so as to avoid blocking the magnetic field from reaching the exhaust gases. As stated earlier, in the preferred embodiment the protrusions in which the magnet system is mounted are anodized aluminum.
• To equalize the exhaust gas flow rate around the azimuth of the chamber, it is preferable to slightly reduce the radial width of the exhaust manifold near the azimuth of the pumping channel and to slightly increase its radial width near the opposite azimuth, i.e., near the azimuth 180 degrees away from the pumping channel.
• The directions of the magnetic fields can be reversed without affecting the operation of the invention. Therefore, all references to north and south poles can be interchanged.
• The illustrated plasma chamber has circular symmetry because it is intended for processing a single, circular semiconductor wafer. In plasma chambers having other geometries, such as chambers for processing multiple substrates or rectangular substrates, the components of the invention such as the deflector and magnet system would be expected to have rectangular or more complex geometries. The term “annular” as used in this patent specification is not intended to limit the described shape to one having a circular inner or outer perimeter, but encompasses rectangular and more complex shapes.
• Alternative Chamber Embodiments of the Present Invention
• FIG. 28 is a cross sectional view of a capacitively coupled, Magnetically Enhanced Reactive Ion Etch (MERIE) chamber having embodiments of the improvements of the present invention.FIG. 28 illustrates anetch processing system2800 similar having the same systems asprocessing system50 ofFIG. 1.Etch processing system2800 includesMERIE chamber2850.MERIE chamber2850 is similar tochamber100 described above with the inclusion of a number of paired electromagnets. For example, fourelectromagnets2810,2812,2814, and2816, typically mounted in a generally rectangular array, one each on the alternating walls ofchamber sidewall106 each having asuitable power supply2830,2832,2834 and2836. For clarity, onlyelectromagnets2810 and2812 and theirrespective power supplies2830 and2832 are illustrated inFIG. 28. Under the control ofcontroller140, the coil pairs2810 and2812 and2814 and2816 cooperatively provide a quasi-static, multi-directional magnetic field which can be stepped or rotated about thewafer10.Electromagnets2810,2812,2814 and2816 generate a controllable magnetic field with a magnitude from about 0 Gauss to about 150 Gauss. Also, the magnitude of the magnetic field can be adjusted to select etch rate and vary ion bombardment. Additional details of MERIE chamber operation are provided in commonly assigned U.S. Pat. No. 4,842,683 entitled, “Magnetic Field-Enhanced Plasma Etch Reactor.”
• FIG. 28 also illustrates an alternative embodiment of thesecond liner118 having only thelower protrusion516.Magnetic confinement system52 is disposed withinlower protrusion516. While themagnetic confinement system52 is illustrated, it is to be appreciated that any of the magnetic confinement systems described above in the section entitled “Plasma Confinement” may be modified for use in the single protrusion embodiment of theliner118.
• FIG. 29 is a cross sectional view of another type of etch chamber having embodiments of the present invention.FIG. 29 illustrates anetch processing system2900 having anetch processing chamber2950.Processing system2900 is similar toprocessing system50 ofFIG. 1 with the addition of asecond RF generator2910 andimpedance matching circuits2915.Processing chamber2950 is similar toprocessing chamber100 with the addition ofparallel plate2920. In operation, RF signals fromRF generators150 and2910 are provided under the control ofcontroller140, viaimpedance matching circuitry151 and2915, respectively, to electrode105 andparallel plate electrode2920, respectively. In one alternative embodiment,RF generators150 and2920 provide RF signals at the same frequency. In an alternative embodiment,RF generators150 and2920 provide RF signals at different frequencies.
• FIG. 30 is a cross sectional view of another processing chamber incorporating embodiments of the present invention.FIG. 30 illustrates an etch processing system3000 having a magnetically enhancedetch chamber3050. Processing system3000 is similar toprocessing system50 with the addition ofcontroller140 operating a magneticfield generating mechanism3010.Processing chamber3050 is similar toprocessing chamber100 with the addition of the magneticfield generating mechanism3010. The magneticfield generating mechanism3010 is disposed on the outer peripheral surface of thecylindrical wall106 of theprocess chamber3050. The magneticfield generating mechanism3010 comprises a plurality of circumferentially arranged permanent magnets having a predetermined polarity which enables generation of a magnetic field parallel to the upper surface of thewafer10, and a driving mechanism for revolving the magnets around theprocessing chamber3050. The magneticfield generating mechanism3010 generates a rotational magnetic field, which rotates about the vertical center axis of theprocess chamber3050 or of thewafer10, in theprocessing volume112 region. Additional details regarding the magneticfield generating mechanism3010 is disclosed in, for example, U.S. Pat. No. 5,980,687.
• FIG. 31 is a cross sectional view of another processing chamber incorporating embodiments of the present invention.FIG. 31 illustrates anetch processing system3100 having anetch chamber3150.Processing system3100 is similar toprocessing system50 with the addition of asecond RF generator3110 andimpedance matching circuitry3105 operated bycontroller140.Processing chamber3050 is similar toprocessing chamber100 with the addition of modifications tolid102 to accommodateantenna3115 mounted to thelid102 and acting as an inductive member for coupling RF power fromRF generator3110 intoprocessing volume112.Impedance matching circuitry3105 couples the RF signal fromgenerator3110 toantenna3115.Nozzles350 have been positioned at the periphery oflid102 to accommodate the efficient inductive coupling of RF energy fromantenna3115 to a plasma formed inprocessing volume112.FIG. 31 illustratesantenna3115 in a flat coil arrangement. Other arrangements ofantenna3115 are possible, such as, for example, a ring arrangement, spiral arrangement, stacked arrangement, or, additionally, multiple antenna segments could be employed with each antenna segment of a multiple antenna segment coupled to an RF generator.
• FIG. 32 is a cross sectional view of another embodiment of an etch chamber having the improvements of the present invention.FIG. 32 illustrates anetch processing system3200 having anetch chamber3250.Processing system3200 is similar toprocessing system50 ofFIG. 1 with the addition of thesecond RF generator3204 andimpedance matching circuit3206.Etch chamber3250 is similar to etchchamber100 with the addition of a flat inductive coil602 and a showerhead style gas injection system instead ofinjector nozzles350. Theetch chamber3250 has a temperature controlledchamber liner104 which regulates the temperature of thechamber liner104 in the manner described above. Thechamber3250 has alid assembly3208 that, with thechamber walls106 andchamber bottom108, define theprocess volume110. Ashowerhead3212 is disposed beneath thelid assembly3208. Process and other gases from agas panel105 pass through a passage in thelid assembly3208 and are dispersed into thechamber volume110 through a plurality of holes in theshowerhead3212. Although shown with afirst liner118 and asecond liner134, theetch chamber3250 may comprise one or both of the first andsecond liners118 and134.Etch chamber3250 also illustrates aliner118 having only asingle protrusion516 withmagnetic system50 disposed therein.
• Chamber Process Window and Representative Critical Dielectric Etch Process
• Embodiments of the improvements of the present invention provide expanded dielectric etch processing capability. The dielectric etch process window enabled by combining the various improvements surpasses the dielectric etch window enabled by conventional etch chambers.
• For example, a magnetically enhanced reactive ion etch chamber having embodiments of the present invention, such as, for example,MERIE chamber2800 ofFIG. 28, has several processing advantages over conventional MERIE processing reactors. Since it is not uncommon for dielectric etch processes to generate polymeric byproducts, several aspects of the present invention cooperatively provide improved polymer adhesion control. First, direct temperature control liners on the walls and cathode help minimize the heating effects caused by plasma cycling. Plasma cycling occurs when the plasma heats portions of the chamber during processing. Polymer adhesion generally decreases with increasing temperature. As a result, those areas heated by plasma cycling are more likely to have polymer depositions that tend to flake off and cause particle contamination. By controlling and uniformly reducing the temperature of the liners, adhesion of the polymeric byproducts to the liners is improved thereby reducing the likelihood that the polymer byproducts will flake off and form particles. Second, use of minimized sizegas inlet nozzles350 ensures that the nozzles are heated by the plasma to temperatures above which the likelihood that by products will form on or adhere to the nozzle openings is reduced. Another advantage of minimizedgas inlet nozzles350 is that because of the small gas inlet nozzle area most of the plasma and by products contact the temperature controlled lid. Like the byproducts that come into contact with the temperature controlled liners, byproducts contacting the temperature-controlled lid will also preferentially deposit on and adhere to the temperature controlled lid and not on the plasma heated minimized size gas distribution nozzles. Third, the cathode and wall temperature controlled liners and the temperature-controlled lid may also further improve byproduct adhesion by incorporating surface texturing features such as those described above in Section IV. Thus, the combination of temperature controlled wall and cathode liners and temperature controlled lid together with minimized gas inlets ensures that most of the plasma processing region comprises temperature controlled surfaces with, preferably, high adhesion texturing.
• Processing chambers having embodiments of the present invention enable dielectric etch processes employing high magnetic fields as high as about 120 G and RF energy up to about 2500 W. Embodiments having a high chamber volume, such as a chamber volume of about 25000 cc, and high capacity vacuum pumping systems such as, for example, a pump system having a pumping speed of from about 1600 l/s to about 2000 l/s enable a high gas flow-low chamber pressure processing regime that is not available in conventional magnetically enhanced and reactive ion etch processing reactors. One advantage of the high pumping speed is an improved capability to control reactive species formation and residence time. Residence time is directly related to the amount of reactive gas dissociation occurring in the plasma. The longer a gas molecule remains exposed to a plasma, the more likely it is that dissociation of that gas molecule will continue. Thus, etch processing reactors having embodiments of the present invention provide desirable plasma gas compositions by enabling improved residence time control.
• Attempts have been previously made and reported on the use of C₄F₆for dielectric etch processes. However, these reports have taught away from using a parallel plate reactor, such as the reactor of the present invention, for dielectric etch using C₄F₆, especially for the linear form of C₄F₆, e.g., hexafluoro-1,3-Butadiene (CF2═CFCF═CF2). Moreover, for the best knowledge of the inventors, none of the reported attempts have been successfully transferred into production lines.
• For example, Yanagida discloses the use of a chain, hexafluorocyclobutene (c—C₄F₆), rather than linear (C₄F₆) in U.S. Pat. No. 5,338,399. On the other hand, in U.S. Pat. No. 5,366,590, Kadamura suggests that either linear of chain C₄F₆may be used, but that a high density plasma, such as that generated using ECR plasma source, inductively coupled plasma source, or transformer coupled plasma source, must be used with either gas. Similarly, in Japanese Application Hei 9[1997]-191002 Fukuda discloses his work with linear C₄F₆, also using high density plasma generated using ECR plasma source. Chatterjee et al., report their work with hexafluoro-2-buttyne and hexafluoro-1,3-Butadiene, also using high density plasma generated by inductively coupled plasma source. Evaluation of Unsaturated Fluorocarbons for Dielectric Etch Applications, Ritwik Chatterjee, Simon Karecki, Laura Pruette, Rafael Reif, Proc. Electrochem. Soc. PV 99-30 (1999). Thus, the prior art teaches that in order to achieve acceptable etch results using linear C₄F₆, such as hexafluoro-1,3-Butadiene, one should use high density plasma, and not low or medium density plasma, such as that achieved using a capacitively coupled plasma source.
• However, the present inventors have shown admirable results of etching using linear C₄F₆in a capacitively coupled plasma source of the invention. The present inventors believe that the high energy generated by high density plasma chambers causes excessive dissociation of the linear C₄F₆. Therefore, they believe that improved results can be achieved using a capacitively coupled chamber, so as to limit the dissociation of the molecules. Also, the present inventors further limit dissociation by using the high pumping capacity enabled by the inventive etch chamber.
• While not desiring to be bound by theory, it is believed that as an etchant gas, such as for example, linear C₄F₆, enters the plasma region of a processing chamber and is exposed to the plasma, it is cracked or dissociated into smaller entities. Generally, for fluorocarbon process gases, shorter residence times provide a capability to produce an increased percentage of the desirable fluorocarbon radical CF_x* while longer residence times produce an increased fraction of the fluorine radical F*. Too much fluorine radical production may reduce photoresist selectivity and/or reduce sidewall profile control. Applicants have found that photoresist selectivity is generally improved with a residence time of less than about 70 ms, and preferably a residence time of less than about 50 ms. Applicants have found that oxide etch rate is improved with a residence time of about 40 ms. Such residence time is made possible by the processing reactor of the present invention and enables etching using linear C₄F₆in a capacitively coupled RIE mode.
• Another useful method of controlling the degree of radical formation in a gas composition is by incorporating an inert gas into the reactive gas composition. It is believed that increasing the amount of inert gas in a reactive gas composition reduces the amount of radicals formed from the reactive gas when the reactive gas/inert gas mixture is exposed to a plasma. Inert gas flow rate to reactive gas flow rate ratios from about 5:1 to about 20:1 are preferred. Total gas flows from about 50 sccm to about 1000 sccm with inert gas flow to reactive gas flow ratios of between about 12:1 to about 16:1 being more preferred.
• Dielectric etch chambers having embodiments of the present invention enable a dielectric etch process window comprising up to 2500 W RF power, magnetic fields from about 0 to about 150 Gauss, total gas flows from 40 sccm to 1000 sccm, chamber pressures from about 20 mT to about 250 mT and liner temperatures ranging from about −20° C. to about 50° C. As described below with regard toFIGS. 33-38, the expanded process window enabled by etch reactors having embodiments of the present invention provide improved dielectric etch process performance, reliability and process tuning versatility for a wide variety of critical dielectric and oxide etch applications.
• A representative self-aligned contact feature is illustrated inFIGS. 33A and 33B, which are not to scale.FIG. 33A represents pre-etch self alignedcontact structure3300.FIG. 33B represents post etch self-alignedcontact structure3305. Both self alignedcontact structures3300 and3305 are formed on asilicon substrate3310. Generally,word lines3315 typically comprise andoxide layer3316, a WSi_xlayer3317 and apolysilicon layer3318.Word lines3315 are covered by aliner layer3320 that is typically formed from silicon nitride. Arepresentative bitline region3325 is illustrated between adjacent word lines3315.Dielectric layer3330 is formed overliner layer3320 and is typically formed from a silicon dioxide, such as, for example, and oxide layer formed from O₃-TEOS based processes. Alternatively, thedielectric layer3330 may be formed from a doped silicon oxide film, such as, for example, a boron and phosphorus doped silicon glass (BPSG). Self alignedcontact feature3300 may include other layers, such as, for example, an anti-reflective coating may be utilized betweenpattern layer3335 anddielectric layer3330.
• Also illustrated in pre-etch self-alignedcontact feature3300 ofFIG. 33A is amask pattern layer3335. When pre-etch self alignedcontact feature3300 is exposed to a suitable etch process,dielectric layer3330 is etched thereby transferring the pattern ofmask layer3335 onto thedielectric layer3330. As illustrated inFIG. 33B, acontact area3340 is formed when a portion ofdielectric layer3330adjacent contact region3325 is removed.
• The exact dimensions of the self alignedcontact structure3300 and3305 will vary depending upon a number of considerations, such as for example, device application, to design rules and critical dimensions ofcontact area3340. For example, for purposes of illustration and not limitation, the self alignedcontact structure3300 may be a 0.25 micron design rule device having anoverall dielectric layer3300 thickness of about 6000 angstroms, aliner layer3320 thickness of about 650 angstroms and amask layer3335 thickness of more than about 7000 angstroms with a pattern opening of about 0.25 microns. The self aligned contact etch processes enabled by the present invention are capable of etching self-aligned contacts having design rules with critical dimensions of less than about 0.25 microns and preferably having critical dimensions of between about 0.1 microns and to less than about 0.18 microns.
• Etching of a self-aligned contact feature is a critical dielectric etch application in part because of the need to avoid etch stop or residual oxide at the word line sidewall. Additionally, a suitable self aligned contact etch process must maximize selectivity to thenitride shoulder3345. Preferably, nitride shoulder selectivity is greater than about 20:1.
• A suitable self aligned contact etch process chemistry comprises a fluorocarbon gas, and an oxygen comprising gas and an inert gas where the total gas flow is more than about 700 sccm and the inert gas comprises more than about 90% of the total gas flow. Reactive gas ratio refers to the ratio of the inert gas flow to the reactive gas flow. In this example, reactive gas ratio would be the ratio of the inert gas flow rate to the combined gas flow rates of the fluorocarbon gas and the oxygen comprising gas. A suitable self-aligned contact etch process has a reactive gas ratio of from about 12:1 to about 16:1 with a preferred reactive gas ratio of about 14.5:1. In a specific embodiment, the ratio of the flow rate of the fluorocarbon gas to the flow rate of the oxygen comprising gas is from about 1.5:1 to about 2:1. The chamber pressure is maintained from about 30 mT to about 40 mT, RF power is maintained from about 1800 W to about 2000 W, the magnetic field is about 50 G and the etch chamber is exhausted at a rate of from about 1600 l/sec to about 2000 l/sec. In a specific preferred embodiment, the etch chamber is exhausted at a rate of from about 48 chamber volumes to about 80 chamber volumes per second. In another preferred embodiment, the substrate support or cathode is maintained at between about 15° C. to about 20° C. while the temperature of a wall or, preferably a temperature controlled liner adjacent the substrate is maintained at about 50° C. In a specific, preferred embodiment the fluorocarbon gas is C₄F₆, the oxygen comprising gas is O₂and the inert gas is Ar.
• A representative high aspect ratio dielectric etch process will now be described with reference toFIGS. 34A and 34B.FIG. 34A illustrates a pre-etch highaspect ratio structure3400 andFIG. 34B illustrates a post etch highaspect ratio structure3405. Neitherstructure3400 nor3405 are illustrated to scale. In this context, a high aspect ratio dielectric etch process is defined as etching features having aspect ratios greater than about 5:1 to about 6:1 while a very high aspect ratio process is defined as etching features having aspect ratios in the range of from about 10:1 to about 20:1. For example, the aspect ratio of thefeature3430 inFIG. 34B is the ratio of thedielectric layer thickness3422 to thefeature width3426. Magnetically enhanced and reactive ion etch chambers having embodiments of the present invention are capable of etching both high and very high aspect ratio features.
• Turning now toFIG. 34A, a representative pre-etch highaspect ratio structure3400 is illustrated that comprises astop layer3415 formed over asilicon substrate3410. Adielectric layer3420, having athickness3422, is formed over thestop layer3415. Amask layer3425 is formed over thedielectric layer3420.Stop layer3415 could be formed from a suitable stop layer material, such as silicon nitride for example. Of course, the specific type of stop layer material will depend upon the device type and design rules of a particular device.
• FIG. 34B illustrates post etch highaspect ratio structure3405 comprising highaspect ratio feature3430. Highaspect ratio feature3430 is formed in thedielectric layer3420 by transferring the pattern ofmask layer3425 ontodielectric layer3420. The pattern ofmask layer3425 is transferred ontodielectric layer3420 by conducting a suitable high aspect ratio dielectric etch process in and etch processing reactor having embodiments of the present invention as described in greater detail below. While aspecific feature width3426 will vary depending upon design rules, in general,feature width3426 varies from about 0.25 micrometers to about 0.1 micrometers. The feature depth corresponds to the thickness ofdielectric layer3420.
• Asdielectric layer thickness3422 increases, the selectivity of the high aspect ratio dielectric etch process to themask layer3425 photoresist material becomes even more critical. The possibility of etch stop also increases with increasingdielectric layer thickness3422. Shrinkingfeature width3426 also poses challenges for maintaining an appropriate sidewall profile ofcontact3430. Bowing or a re-entrant sidewall profile ofcontact3430 can lead to an unacceptably small diameter at the bottom ofcontact3430adjacent stop layer3415. High aspect ratio contact etching is a critical dielectric etch process because of the challenges posed by shrinking feature width, increasing contact depth, selectivity to photoresist materials and sidewall profile control.
• High aspect ratio feature etching may also be complicated by adielectric layer3420 comprising a doped silicon oxide such as, for example, BPSG.Dielectric layers3420 comprising a plurality of dielectric materials forming a multilevel structure also pose many challenges to high aspect ratio feature etching. One example of such a multilevel structure is a feature structure having adielectric layer3420 comprising multiple intermediate stop layers at different depths, such as for example, those features seen mainly in the peripheral areas of stack capacitor DRAM structures.
• The exact dimensions of the highaspect ratio structure3400 will vary depending upon a number of considerations, such as for example, the device application, and the design rules of a particular device. For example, the representative highaspect ratio structure3400 may have a mask with3426 of about 0.25 microns, amask layer3425 thickness of about 7000 angstroms, adielectric layer thickness3422 of about 15,000 angstroms and astop layer3415 thickness of about 500 angstroms. It is to be appreciated that the above specific dimensions or for illustration and not for limitation. Magnetically enhanced and reactive ion etch chambers having embodiments of the present invention are capable of etching high aspect ratio and very high aspect ratio features having aspect ratios from about 5:1 to about 20:1 with critical dimensions (i.e., contact with3426, for example) of from about 0.25 microns to about 0.1 microns.
• Suitable high aspect ratio dielectric feature etch process window that meets the above challenges includes high magnetic field of up to about 100 G, high RF power of up to about 2000 W and high inert gas flow of between about 500 sccm and about 1000 sccm. Increased magnetic field provides increased selectivity to the photomask material in the mask layer and reduces the likelihood of sidewall bowing. Increased inert gas flow provides a wider range of reactive gas dilution thereby decreasing residence time and reactive species formation which in turn further improve photoresist selectivity. In addition, the increased pump speeds of the present invention described above with regard to self aligned contact etching may also be employed in high aspect ratio etching to further improve control of residence time and reactive species a formation.
• The suitable high aspect ratio dielectric etch process comprises a fluorocarbon gas, and oxygen comprising gas and an inert gas where the total gas flow is more than about 700 sccm an and the inert gas comprises more than about 90 percent of the total gas flow. A suitable high aspect ratio dielectric etch process has a reactive gas ratio of from about 10:1 to about 15:1. In a specific embodiment, the ratio of the flow rate of the fluorocarbon gas to the flow rate of the oxygen comprising gas is about 1.5:1. In a specific embodiment the gas composition used for etching comprises a fluorocarbon gas flow that provides from about 3 percent to about 6 percent of the total gas flow, an oxygen comprising gas comprising from about one percent to about four percent of the total gas flow and an inert gas making up more than 90 percent of the total gas composition flow.
• In the specific embodiment, the chamber pressure is maintained from about 20 mT to about 60 mT, the RF power is from about 1,000 watts to about 2,000 watts, the magnetic field is maintained at about 100 G, and the etch chamber is exhausted at a rate from about 48 chamber volumes to about 80 chamber volumes per second. In another preferred embodiment, the substrate support is maintained at about −20 degrees C while a wall or preferably, direct temperature control liner, is maintained at about 15 C. In a specific preferred embodiment, the fluorocarbon gas is C₄F₆, the oxygen comprising gas is0₂and the inert gas is argon.
• FIGS. 35A and 35B illustrate, respectively, representative pre-and post-metal viaetch structures3500 and3505. Generally, metal via etch processes are important in forming interconnect structures between metal layers in an electronic device. Typically, the via formed in the dielectric material during a metal via etch is later filled by a metal such as, for example, a tungsten plug commonly used in aluminum based metalization schemes. Suitable metal via etch processes are selective to thebarrier layer3515 or alternatively, selective to theunderlying metal layer3510.
• FIG. 35A represents pre-etch metal viafill structure3500 formed overmetal layer3510. Abarrier layer3515, such as for example, a layer comprising titanium and titanium nitride, is formed overmetal layer3510 and separatesdielectric layer3520 frommetal layer3510. Thedielectric layer3520 is typically a TEOS based silicon dioxide and may, alternatively, be an HDP-CVD silicon dioxide film as well.FIG. 35A also illustrates the use of ananti-reflective coating layer3525 undermasking layer3530.
• The specific dimensions of metal viaetch structures3500 and3505 such as the thickness ofdielectric layer3520 and the width of contact via3535 vary depending upon the type of via structure and upon the design rules used in a particular device. For example, the 0.25 micron feature device may have adielectric layer3520 about 10,000 angstroms thick and formed from TEOS with abarrier layer3515 about 500 angstroms thick and formed from titanium nitride. Etch reactors having embodiments of the present invention are capable of etching contact vias having critical dimensions of from about 0.25 microns to about 0.1 microns and vias having aspect ratios of up to about 5:1.
• A suitable metal via etch gas composition chemistry comprises a fluorocarbon gas, and an oxygen comprising gas and an inert gas wherein the total gas flow is less than about 500 sccm. In a particular embodiment, the inert gas flow rate provides about 85 percent of the total gas composition flow and the ratio of the inert gas to the reactive gases (i.e., the ratio of the inert gas flow rate to the combined flow rates of the fluorocarbon gas and the oxygen comprising gas) is between about 4:1 to about 6:1. In a specific preferred embodiment, the fluorocarbon gas provides about 9.5 percent of the total gas composition flow, the chamber is maintained at about 20 mT, the RF power is about 1500 watts, the magnetic field is about 50 Gauss and the substrate support and a wall, or preferably a temperature control liner adjacent the substrate support, are maintained at about the same temperature.
• In an alternative embodiment, the gas composition for a metal via etch process comprises a first fluorocarbon gas having a carbon to fluorine ratio of 1:3, a second fluorocarbon gas having a carbon to fluorine ratio of about 2:1 and any inert gas wherein the total gas flow of the gas composition is from about 200 sccm and to about 300 sccm. In a specific preferred embodiment, the first fluorocarbon gas comprises from about 14 percent to about 18 percent of the total gas composition flow, and the second fluorocarbon gas comprises from about 13 percent to about 16 percent of the total flow of the gas composition. In a specific preferred embodiment, the ratio of the first fluorocarbon gas flow rate to the inert gas flow rate and the ratio of the second fluorocarbon gas flow rate to the inert gas flow rate is from about 0.2 to about 0.25. In another specific embodiment, the first fluorocarbon gas is C₂F₆, the second fluorocarbon gas is C₄F₈, the inert gas is argon, the chamber is maintained at below about 200 mT, the RF power is about 1800 watts, the magnetic field is about 30 G and the chamber is exhausted at from about 1,600 liters per second to about 2,000 liters per second.
• FIGS. 36A and 36B illustrate feature structures representative of a mask open application.FIGS. 36A and 36B are not drawn to scale. Some mask materials, such as for example, silicon nitride, are considerably more difficult to etch than other mask materials and are referred to as “hard masks.”FIG. 36A illustrates pre-hardmask etch structure3600. While hardmasked layer3615 may be formed over a wide variety of other layers and materials,FIGS. 36A and 36B illustrate ahard mask layer3615 deposited directly on asilicon substrate3610 formed from a suitable hard mask material, such as for example, silicon nitride. Nitride hard masks comprise, for example, active area hard mask etching and deed conductor hard mask etching.FIG. 36A also illustrates the use of anantireflective coating layer3620 belowphotomask pattern layer3625.FIG. 36B illustrates post hardmask etch structure3605 where the pattern ofphotomask layer3625 has been transferred intohard mask layer3615 by a suitable hard mask etch process performed in and etch processing chamber having embodiments of the present invention.
• The suitable hard mask open process chemistry comprises a gas composition comprising a hydrofluorocarbon gas, a fluorocarbon gas and an oxygen comprising gas wherein the total gas flow of the gas composition is from about 50 sccm to about 200 sccm. In a specific embodiment, the hydrofluorocarbon gas comprises more than about half of the total gas composition flow rate and the oxygen comprising gas flow rate comprises less than about 15 percent of the total gas composition flow rate. In another specific embodiment, the ratio of the flow rate of the hydrofluorocarbon gas to the flow rate of the fluorocarbon gas is about 1.5:1. In another specific embodiment, the ratio of the combined hydrofluorocarbon gas flow rate and the fluorocarbon gas flow rate to the flow rate of the oxygen comprising gas is about 5.5:1.
• In a specific preferred embodiment, the hydrofluorocarbon gas is a CHF₃, the fluorocarbon gas is a CF₄, the oxygen comprising gas is0₂, the pressure in the process chamber is maintained from about 20 mT to about 80 mT and the RF power is about 500 watts. In yet another specific embodiment, the substrate support is maintained about 15 degrees Celsius higher than a temperature of an adjacent wall, or preferably, a temperature controlled liner.
• FIGS. 37A and 37B illustrate, respectively,pre-etch spacer structure3700 and postetch spacer structure3705.FIGS. 37A and 37B are not illustrated to scale.Pre-etch spacer structure3700 illustrates afeature3715 formed over anunderlayer3720 on top of asilicon substrate3710. Adielectric layer3725 is formed over both thefeature3715 and theunderlayer3720. Postetch spacer structure3705 ofFIG. 37B is formed after conducting a suitable spacer etch process as described in greater detail below. In postspacer etch structure3705,spacer feature3725 is formed by etchingdielectric layer3725 to expose the top portion of thefeature3715 and remove most of theunderlayer3720. In a representative spacer structure,feature3715 could be formed from polysilicon and theunderlayer3720 could be formed from silicon dioxide.
• In general, spacer etch processes may be divided into two categories based upon selectivity to theunderlayer3720. For example, in the illustrated spacer structure described above, the spacer etch process is selective to an underlying silicon dioxide layer. Alternatively, when removal of bothdielectric layer3725 anunderlying layer3720 is desired, a spacer etch process selective to thesilicon substrate3710 may be used in order to etch bothdielectric layer3725 andunderlying layer3720 before stopping upon reachingsilicon substrate3710.
• The gas composition used to form a suitable spacer etch process chemistry comprises a hydrofluorocarbon gas, a fluorocarbon gas, an oxygen comprising gas and an inert gas with a total gas flow of the gas composition is from about 50 sccm to about 200 sccm. In a specific embodiment, the hydrofluorocarbon gas flow comprises more than about 40 percent of the total gas flow and the oxygen comprising gas comprises less than about 5 percent of the total gas composition flow rate. In another specific embodiment, the ratio of the hydrofluorocarbon gas flow to the fluorocarbon gas flow is about 2.5:1. In yet another specific embodiment, the combined flow rate of the hydrofluorocarbon gas and the fluorocarbon gas to the flow rate of the inert gas is about 1.75:1.
• In a specific preferred embodiment, the fluorocarbon gas is CF₄, the hydrofluorocarbon gas is CHF₃, the oxygen comprising gas is0₂, the inert gas is argon, the pressure of the etch chamber is maintained at between about 20 mT to about 80 mT, the RF power is about 400 watts, the substrate support is maintained at a temperature about 25 degrees Celsius higher than an adjacent wall, or preferably, an adjacent direct temperature controlled liner.
• FIGS. 38A and 38B illustrate representative structures for etching dual damascene features.FIG. 38A illustrates pre-dual damascenedielectric etch structure3800 andFIG. 38B illustrates post dual damascenedielectric etch structure3805.FIGS. 38A and B are not illustrated to scale.
• FIG. 38A illustrates a basic dual damascene structure formed over in metal layer, such as for example, acopper layer3810. Two dielectric layers, namely trenchdielectric layer3830 and viadielectric layer3820, are etched during a suitable dual damascene dielectric etch process, such as those discussed in more detail below. Abottom nitride layer3815 separates thecopper layer3810 from the viadielectric layer3820.Intermediate nitride layer3825 separates thetrench dielectric layer3830 from the viadielectric layer3820. In some dual damascene etch processes, theintermediate nitride layer3825 is used as a stop layer for etching thetrench dielectric layer3830 and thebottom nitride layer3815 is used as a stop layer for etching the viadielectric layer3820.FIG. 38B illustrates post dualdamascene etch structure3805 that includes a viafeature3850 and aninterconnect feature3855. Typically, the viafeature3850 and theinterconnect feature3855 are filled by subsequent metalization processes.
• There are at least three fundamental process flows used to form dual damascene features: self aligned, trench first, and via first. While other structures may be and are used, in general, typical dual damascene etch processes begin with a pre-etch structure, such asstructure3800 ofFIG. 38A, and finish with a structure having a viafeature3850 and aninterconnect feature3855 as illustrated inFIG. 38B.
• In a self aligned dual damascene process, a via pattern is etched first by openingintermediate nitride layer3825. During a subsequent etch step that usesbottom nitride layer3815 as an etch stop layer, both the viafeature3850 and theinterconnect feature3855 are formed. Finally, thebottom nitride layer3815 is removed to exposecopper layer3810.
• In a trench first dual damascene process, themask pattern layer3835 forms the pattern for theinterconnect feature3855 and theupper portion3860 of the viafeature3850. The resulting intermediate structure comprisesinterconnect3855 and the upper portion of viafeature3860. This intermediate structure is then patterned and etched to form the lower portion of via feature3865 using bottom nitride layer of3815 as an etch stop layer. A subsequent etch step is then used to removebottom nitride layer3815 and expose thecopper layer3810.
• In a via first dual damascene process, a via pattern is formed by themask pattern layer3835. The via pattern is subsequently transferred to both of thedielectric layers3830 and3820 and to theintermediate nitride layer3825. This step forms an intermediate structure comprising the lower portion3865 of viastructure3850. Next, a trench mask pattern is formed over this intermediate structure to pattern the trenches, namely theinterconnect feature3855 and the upper portion ofcontact feature3860. Thebottom nitride layer3815 is subsequently removed exposing thecopper layer3810.
• The exact dimensions of thedual damascene structures3800 and3805 will vary depending upon a number of considerations, such as for example, the type of dual damascene process sequence and the design rules of a particular device. The particular design rules determine the dimensions fortrench feature3855, viafeature3850 and, more importantly, the critical dimension of contact region3865. Etch process chambers having embodiments of the present invention are capable of etching dual damascene structures having critical dimensions of about 0.3 microns to about 0.25 microns and even structures having critical dimensions of about 0.1 microns to about 0.2 microns. A suitable dual damascene trench etch process chemistry comprises a fluorocarbon gas having a carbon to fluorine ratio of about 1:3 and a gas comprising carbon and oxygen. In a preferred embodiment, most of the gas composition comprises a gas comprising carbon and oxygen with the total flow of the gas composition being from between about 200 sccm to about 400 sccm. In a specific preferred embodiment, at least about 60 percent of the gas composition comprises a gas comprising oxygen and carbon. In another specific embodiment, the ratio of the flow rate of the gas comprising oxygen and carbon to the flow rate of the fluorocarbon gas is about 1.67:1. In yet another specific preferred embodiment, the fluorocarbon gas is C₂F₆, the gas comprising oxygen and carbon is CO, the pressure to processing chamber is maintained at between about 100 mT to about 200 mT, the magnetic field in the processing region is about 30 G and the RF power is about 1500 watts.
• In an alternative embodiment where the dual damascene structure comprises a nitride stop layer, a suitable dual damascene etch process chemistry comprises a gas composition comprising a polymerizing fluorocarbon having a C:F ratio of about 1:2, and oxygen comprising gas and an inert gas. In a specific preferred embodiment, the inert gas comprises more than about 90 percent of the total gas composition flow, and the oxygen comprising gas comprises less than about 1 percent of the total gas composition flow. In another specific preferred embodiment, the ratio of the inert gas flow to the combined flow rates of the polymerizing fluorocarbon gas and the oxygen comprising gas is from about 20:1 to about 22:1. In a specific preferred embodiment the polymerizing fluorocarbon gas is C₄F₈and the oxygen comprising gas is0₂and the ratio of the C₄F₈flow rate to the0₂flow rate is about 3:1 about 4:1. In a specific preferred embodiment, the gas composition comprises a C₄F₈,0₂and Ar wherein the Ar flow rate is more than about 95 percent of the total gas composition flow rate, the C₄F₈flow rate comprises more than about three percent of the total gas composition flow rate, the chamber is maintained at about 80 mT, the RF power level is about 1800 watts, the magnetic field in a processing region is about 20 G, the substrate support is maintained at about 10 degrees Celsius higher than the temperature of an adjacent wall or, preferably, a temperature controlled liner.
• One suitable dual damascene via etch chemistry comprises a gas composition comprising a fluorocarbon gas having a C:F ratio of about 2:3, and oxygen comprising gas and an inert gas. In a specific preferred embodiment, the etch chamber is maintained between about 30 mT to about 80 mT, the total gas composition flow rate is from about 300 sccm to about 500 sccm an and the ratio of the inert gas flow rate to the combined flow rates of the fluorocarbon gas having a C:F ratio of about 2:3 and an oxygen comprising gas is from about 5:1 to about 7:1 and more preferably, about 6:1. In a specific preferred embodiment, the fluorocarbon gas having a C:F ratio of about 2:3 is C₄F₆, the oxygen comprising gas is0₂and inert gas is argon, the C₄F₆comprises about 5% to about 9% of the total gas composition flow and the inert gas flow comprises more than about 80 percent of the gas composition flow, the chamber is maintained at about 50 mT, the RF power is about 1800 watts and a magnetic field in the processing region is about 50 G.
• In another alternative embodiment, a two-step dual damascene via etch process may be used. A suitable to two-step dual damascene via etch process chemistry comprises a gas composition comprising a polymerizing fluorocarbon gas, a hydrofluorocarbon gas, an oxygen comprising gas and an inert gas wherein the ratio of the inert gas flow to the combined gas flows of the polymerizing fluorocarbon gas, the hydrofluorocarbon gas and the oxygen comprising gas is from about 4:1 to about 6:1; and the polymerizing fluorocarbon gas used in the second step is greater than the first step. In a specific preferred embodiment of a suitable two-step dual damascene via process, the first step gas composition comprises less than about three percent polymerizing fluorocarbon gas, about 4 percent to about 5 percent oxygen comprising gas, about 7 percent to about nine percent hydrofluorocarbon gas and more than about 80 percent inert gas while the second step comprises more than about 4 percent polymerizing fluorocarbon gas, about 4 percent to about 5 percent oxygen comprising gas, about 7 percent to about 8 percent hydrofluorocarbon gas and more than about 80 percent inert gas. In a specific preferred embodiment, the total gas composition flow rate in each etch step is from about 500 sccm to about 1,000 sccm, the pressure is about 50 mT, the RF power level is about 2,000 watts and the magnetic field apply to the processing region is about 15 G. In another specific preferred embodiment, the polymerizing fluorocarbon gas is C₄F₆, the hydrofluorocarbon gas is CHF₃, the oxygen comprising gas is O₂and the inert gas is Ar.
• It is to be appreciated that each of the alternative etch process chamber embodiments and critical etch processes described above may incorporate aspects of the high exhaust pump rate and reduced reactive species residence time control feature of the present invention.
• The terms “below”, “above”, “bottom”, “top”, “up”, “down”, “first”, and “second” and other positional terms are shown with respect to the embodiments in the figures and may be varied depending on the relative orientation of the processing system.
• Furthermore, in this specification, including particularly the claims, the use of “comprising” with “a” or “the”, and variations thereof means that the item(s) or list(s) referenced includes at least the enumerated item(s) or list(s) and furthermore may include a plurality of the enumerated item(s) or list(s), unless otherwise stated.
• Although the embodiment of the invention which incorporate the teachings of the present invention which has been shown and described in detail herein, those skilled in the art can readily devise other varied embodiments which still incorporate the teachings and do not depart from the spirit of the invention.

Claims (18)

1. A method of etching features on a dielectric layer on a substrate with enhanced etch selectivity, comprising:

(a) disposing a substrate in a processing region of a plasma etch chamber;

(b) controlling the temperature of a substrate support;

(c) flowing a gas composition comprising hexafluoro-1,3-Butadiene, oxygen and argon, into the processing region;

(d) capacitively coupling RF energy into the processing region to form a plasma from the gas composition;

(e) continuously evacuating the chamber at a pumping rate of a vacuum pump sufficient to evacuate said chamber at a rate of 48 to 80 chamber volumes per second.

2. The method ofclaim 1 wherein said pumping rate is sufficient to provide a residence time of reactive species in the processing region of less than about 70 ms.

3. A method of etching features on a dielectric layer on a substrate with enhanced etch selectivity, comprising:

(a) disposing a substrate in a processing region of a plasma etch chamber;

(b) controlling the temperature of a substrate support;

(c) flowing a gas composition comprising hexafluoro-1,3-Butadiene, oxygen and argon, into the processing region;

(d) capacitively coupling RF energy into the processing region to form a plasma from the gas composition;

(e) continuously evacuating the chamber using a pump rated at 1600 liters/sec. or higher.

4. The method ofclaim 3, wherein said flowing a gas composition is performed at total gas flow rate in a range from 40 sccm to 1000 sccm.

5. The method ofclaim 3, wherein flow ratio of argon to hexafluoro-1,3-Butadiene is from about 5:1 to about 20:1.

6. The method ofclaim 3, wherein said evacuating comprises maintaining the chamber pressure from about 20 mT to about 250 mT.

7. A method of etching features on a dielectric layer on a substrate with enhanced etch selectivity, comprising:

(a) disposing a substrate in a processing region of a plasma etch chamber;

(b) controlling the temperature of a substrate support;

(c) flowing a gas composition comprising hexafluoro-1,3-Butadiene, oxygen and argon, into the processing region;

(d) capacitively coupling RF energy into the processing region to form a plasma from the gas composition; and

(e) continuously evacuating the chamber at a pumping rate of a vacuum pump of at least about 1600 liter per second.

8. The method ofclaim 7, wherein said flowing a gas composition is performed at total gas flow rate in a range from 40 sccm to 1000 sccm.

9. The method ofclaim 7, wherein flow ratio of argon to hexafluoro-1,3-Butadiene is from about 5:1 to about 20:1.

10. The method ofclaim 7, wherein said evacuating comprises maintaining the chamber pressure from about 20 mT to about 250 mT.

11. A method of performing a self-aligned contact etch process in a semiconductor substrate with a plasma etch reactor, comprising:

(a) disposing the substrate in a processing region of the plasma reactor;

(b) flowing a gas composition comprising hexafluorobutadiene, oxygen and argon;

(c) capacitively coupling RF energy into the processing region to form a plasma from the gas composition; and

(d) continuously evacuating said chamber at a vacuum pump rate of at least about 1600 liters per second.

12. The method ofclaim 11, wherein said flowing a gas composition is performed at total gas flow rate in a range from 40 sccm to 1000 sccm.

13. The method ofclaim 11, wherein flow ratio of argon to hexafluoro-1,3-Butadiene is from about 5:1 to about 20:1.

14. The method ofclaim 11, wherein said evacuating comprises maintaining the chamber pressure from about 20 mT to about 250 mT.

15. A method of performing a self-aligned contact etch process on a semiconductor substrate with a plasma etch reactor, comprising:

(a) disposing the substrate in a processing region of the plasma reactor;

(b) flowing a gas composition comprising hexafluorobutadiene, oxygen and argon;

(c) capacitively coupling RF energy into processing region for form a plasma from the gas composition; and

(d) continuously evacuating the chamber using a pump rated at 1600 liters/sec. or higher.

16. The method ofclaim 15, wherein said flowing a gas composition is performed at total gas flow rate in a range from 40 sccm to 1000 sccm.

17. The method ofclaim 15, wherein flow ratio of argon to hexafluoro-1,3-Butadiene is from about 5:1 to about 20:1.

18. The method ofclaim 15, wherein said evacuating comprises maintaining the chamber pressure from about 20 mT to about 250 mT.

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