US20120180954A1 - Semiconductor processing system and methods using capacitively coupled plasma - Google Patents

Abstract

Substrate processing systems are described that have a capacitively coupled plasma (CCP) unit positioned inside a process chamber. The CCP unit may include a plasma excitation region formed between a first electrode and a second electrode. The first electrode may include a first plurality of openings to permit a first gas to enter the plasma excitation region, and the second electrode may include a second plurality of openings to permit an activated gas to exit the plasma excitation region. The system may further include a gas inlet for supplying the first gas to the first electrode of the CCP unit, and a pedestal that is operable to support a substrate. The pedestal is positioned below a gas reaction region into which the activated gas travels from the CCP unit.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS
• This application is a nonprovisional of, and claims the benefit of the filing date of, U.S. Provisional Patent Application No. 61/433,633, entitled “SEMICONDUCTOR PROCESSING SYSTEM AND METHODS USING CAPACITIVELY COUPLED PLASMA, filed Jan. 18, 2011, the entire disclosure of which is incorporated herein by reference for all purposes.
BACKGROUND OF THE INVENTION
• Plasma deposition and etching processes for fabricating semiconductor integrated circuits have been in wide use for decades. These processes typically involve the formation of a plasma from plasma-generating gases that are exposed to electric fields of sufficient power inside the processing chamber to cause the gases to ionize. The temperatures needed to form these gases into plasmas can be much lower than needed to thermally ionize the same gases. Thus, plasma generation processes can be used to generate reactive radical and ion species from the starting gases at significantly lower chamber processing temperatures than is possible by simply heating the gases. This allows the plasma to deposit and/or etch materials from substrate surfaces without raising the substrate temperature above a threshold that will melt, decompose, or otherwise damage materials on the substrate.
• Exemplary plasma deposition processes include plasma-enhanced chemical vapor deposition (PECVD) of dielectric materials such as silicon oxide on exposed surfaces of a substrate wafer. Conventional PECVD involves the mixing together of gases and/or deposition precursors in the processing chamber and striking a plasma from the gases to generate reactive species that react and deposit material on the substrate. The plasma is typically positioned close to the exposed surface of the substrate to facilitate the efficient deposition of the reaction products.
• Similarly, plasma etching processes include exposing selected parts of the substrate to plasma activated etching species that chemically react and/or physically sputter materials from the substrate. The removal rates, selectivity, and direction for the plasma etched materials can be controlled with adjustments to the etchant gases, plasma excitation energy, and electrical bias between the substrate and charged plasma species, among other parameters. Some plasma techniques, such as high-density plasma chemical vapor deposition (HDP-CVD), rely on simultaneous plasma etching and deposition to create features on the substrate.
• While plasma environments are generally less destructive to substrates than high-temperature deposition environments, they still create fabrication challenges. Etching precision can be a problem with energetic plasmas that over-etch shallow trenches and gaps. Energetic species in the plasmas, especially ionized species, can create unwanted reactions in a deposited material that adversely affect the material's performance. Thus, there is a need for systems and methods to provide more precise control over the plasma components that make contact with a substrate wafer during fabrication.
BRIEF SUMMARY OF THE INVENTION
• Systems and methods are described for improved control of the environment between a plasma and the surfaces of a substrate wafer that are exposed to plasma and/or its effluents. The improved control may be realized at least in part by an ion suppression element positioned between the plasma and the substrate that reduces or eliminates the number of ionically-charged species that reach the substrate. Adjusting the concentration of ion species that reach the substrate surface allows more precise control of the etch rate, etch selectivity, and deposition chemistry (among other parameters) during a plasma assisted etch and/or deposition on the substrate.
• In some examples, the ion suppression element may be part of the gas/precursor delivery equipment of a substrate processing chamber. For example, a showerhead positioned inside the chamber between a plasma region and the substrate may act as both a distribution component for gases and precursors as well as an ion suppressor that reduces the amount of ionized species traveling through the showerhead from the plasma region to the substrate. In additional examples, the ion suppression element may be a partition between the plasma region and the substrate that has one or more openings through which plasma effluents may pass from the plasma region to the substrate. The size, position and geometry of the openings, the distance between the partition and the substrate, and the electrical bias on the partition, among other characteristics, may be selected to control the amounts of charged species reaching the substrate. In some instances the partition may also act as an electrode that helps generate and define the plasma region in the processing chamber.
• Embodiments of the invention include a substrate processing system that has a capacitively coupled plasma (CCP) unit positioned inside the process chamber. The CCP unit may include a plasma excitation region formed between a first electrode and a second electrode. The first electrode may include a first plurality of openings to permit a first gas to enter the plasma excitation region, and the second electrode may include a second plurality of openings to permit an activated gas to exit the plasma excitation region. The system may further include a gas inlet for supplying the first gas to the first electrode of the CCP unit, and a pedestal that is operable to support a substrate. The pedestal is positioned below a gas reaction region into which the activated gas travels from the CCP unit.
• Embodiments of the invention further include additional substrate processing systems. These systems may include a gas inlet for supplying a first gas to a processing chamber, an electrode comprising a plurality of openings, and a showerhead. The showerhead may include a first plurality of channels that permit the passage of an activated gas to a gas reaction region in the processing chamber, and a second plurality of channels that permit passage of a second gas to the gas reaction region. The activated gas is formed in a plasma excitation region between the electrode and the showerhead, which also acts as a second electrode. The systems may further include a pedestal positioned below the gas reaction region that is operable to support a substrate.
• Embodiments of the invention still further include substrate processing systems having an ion suppressor. These systems may include a gas inlet for supplying a first gas to a processing chamber, an electrode with a first plurality of openings, and the ion suppressor. The ion suppressor may include an electrically conductive plate having a second plurality of openings that permit the passage of an activated gas to a gas reaction region in the processing chamber. The activated gas is formed in a plasma excitation region between the electrode and the ion suppressor. These systems may further include a pedestal, positioned below the gas reaction region, that is operable to support a substrate.
• Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the invention. The features and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
• A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference numerals are used throughout the several drawings to refer to similar components. In some instances, a sublabel is associated with a reference numeral and follows a hyphen to denote one of multiple similar components. When reference is made to a reference numeral without specification to an existing sublabel, it is intended to refer to all such multiple similar components.
• FIG. 1 shows a simplified cross-sectional view of a processing system that includes a processing chamber having CCP unit and showerhead according to embodiments of the invention;
• FIG. 2 shows a simplified perspective view of a processing system that includes a processing chamber having a CCP unit and showerhead according to embodiments of the invention;
• FIG. 3 shows a simplified schematic of the gas flow paths of a pair of gas mixtures through a processing system according to embodiment of the invention;
• FIG. 4 shows a simplified cross-sectional view of a processing system that includes a processing chamber having a showerhead that also acts as an ion suppression element;
• FIG. 5 shows a simplified cross-sectional view of a processing system that includes a processing chamber with an ion suppression plate partitioning a plasma region from gas reaction region according to embodiments of the invention;
• FIG. 6A shows a simplified perspective view of an ion-suppression element according to embodiments of the invention;
• FIG. 6B shows a simplified perspective view of a showerhead that also act as an ion-suppression element according to embodiments of the invention;
• FIG. 7A shows some exemplary hole geometries for the openings in an ion-suppression element according to embodiments of the invention;
• FIG. 7B shows a schematic of a hole geometry opening according to embodiments of the invention; and
• FIG. 8 shows an exemplary configuration of opposing openings in a pair of electrodes that help define a plasma region in a processing chamber according to embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
• Systems and methods are described for the generation and control of a plasma inside a semiconductor processing chamber. The plasma may originate inside the processing chamber, outside the processing chamber in a remote plasma unit, or both. Inside the chamber, the plasma is contained and separated from the substrate wafer with the help of an ion suppression element that is positioned between the plasma and the substrate wafer. In some instances, this ion suppression element may also function as part of a plasma generation unit (e.g., an electrode), a gas/precursor distribution system (e.g., a showerhead), and/or another component of the processor system. In additional instances, the ion suppression element may function primarily to define a partition between a plasma generation region and a gas reaction region that etches and/or deposits material on exposed surfaces of the substrate wafer.
• The ion suppression element functions to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with substrate. It should be noted that the complete elimination of ionically charged species in the reaction region surrounding the substrate is not always the desired goal. In many instances, ionic species are required to reach the substrate in order to perform the etch and/or deposition process. In these instances, the ion suppressor helps control the concentration of ionic species in the reaction region at a level that assists the process.
• Exemplary Processing System Configurations
• Exemplary processing system configurations include an ion suppressor positioned inside a processing chamber to control the type and quantity of plasma excited species that reach the substrate. In some embodiments the ion suppressor unit may be a perforated plate that may also act as an electrode of the plasma generating unit. In additional embodiments the ion suppressor may be the showerhead that distributes gases and excited species to a reaction region in contact with the substrate. In still more embodiments ion suppression may be realized by a perforated plate ion suppressor and a showerhead, both of which plasma excited species pass through to reach the reaction region.
• FIGS. 1 and 2 show simplified cross-sectional and perspective views, respectively, of a processing system that includes both anion suppressor110 as part of a capacitively coupled plasma (CCP)unit102 and ashowerhead104 that may also contribute to ion suppression. The processing system may also optionally include components located outside theprocessing chamber100, such asfluid supply system114. Theprocessing chamber100 may hold an internal pressure different than the surrounding pressure. For example, the pressure inside the processing chamber may be about 10 mTorr to about 20 Torr.
• TheCCP unit102 may function to generate a plasma inside theprocessing chamber100. The components of theCCP unit102 may include a lid orhot electrode106 and an ion suppression element110 (also referred to herein as an ion suppressor). In some embodiments, thelid106 andion suppressor110 are electrically conductive electrodes that can be electrically biased with respect to each other to generate an electric field strong enough to ionize gases between the electrodes into a plasma. Anelectrical insulator108, may separate thelid106 and theion suppressor110 electrodes to prevent them from short circuiting when a plasma is generated. The plasma exposed surfaces of thelid106,insulator108, andion suppressor110 may define aplasma excitation region112 in theCCP unit102.
• Plasma generating gases may travel from agas supply system114 through agas inlet116 into theplasma excitation region112. The plasma generating gases may be used to strike a plasma in theexcitation region112, or may maintain a plasma that has already been formed. In some embodiments, the plasma generating gases may have already been at least partially converted into plasma excited species in a remote plasma system (not shown) positioned outside theprocessing chamber100 before traveling downstream though theinlet116 to theCCP unit102. When the plasma excited species reach theplasma excitation region112, they may be further excited in theCCP unit102, or pass through the plasma excitation region without further excitation. In some operations, the degree of added excitation provided by theCCP unit102 may change over time depending on the substrate processing sequence and/or conditions.
• The plasma generating gases and/or plasma excited species may pass through a plurality of holes (not shown) inlid106 for a more uniform delivery into theplasma excitation region112. Exemplary configurations include having theinlet116 open into agas supply region120 partitioned from theplasma excitation region112 bylid106 so that the gases/species flow through the holes in thelid106 into theplasma excitation region112. Structural and operational features may be selected to prevent significant backflow of plasma from theplasma excitation region112 back into thesupply region120,inlet116, andfluid supply system114. The structural features may include the selection of dimensions and cross-sectional geometry of the holes inlid106 that deactivates backstreaming plasma, as described below inFIGS. 7A and 7B. The operational features may include maintaining a pressure difference between thegas supply region120 andplasma excitation region112 that maintains a unidirectional flow of plasma through theion suppressor110.
• As noted above, thelid106 and theion suppressor110 may function as a first electrode and second electrode, respectively, so that thelid106 and/orion suppressor110 may receive an electric charge. In these configurations, electrical power (e.g., RF power) may be applied to thelid106,ion suppressor110, or both. For example, electrical power may be applied to thelid106 while theion suppressor110 is grounded. The substrate processing system may include aRF generator140 that provides electrical power to thelid106 and/orion suppressor110. The electrically chargedlid106 may facilitate a uniform distribution of plasma (i.e., reduce localized plasma) within theplasma excitation region112. To enable the formation of a plasma in theplasma excitation region112,insulator108 may electrically insulatelid106 andion suppressor110.Insulator108 may be made from a ceramic and may have a high breakdown voltage to avoid sparking TheCCP unit102 may further include a cooling unit (not shown) that includes one or more cooling fluid channels to cool surfaces exposed to the plasma with a circulating coolant (e.g., water).
• Theion suppressor110 may include a plurality ofholes122 that suppress the migration of ionically-charged species out of theplasma excitation region112 while allowing uncharged neutral or radical species to pass through theion suppressor110 into an activatedgas delivery region124. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through theholes122. As noted above, the migration of ionic species through theholes122 may be reduced, and in some instances completely suppressed. Controlling the amount of ionic species passing through theion suppressor110 provides increased control over the gas mixture brought into contact with the underlying wafer substrate, which in turn increases control of the deposition and/or etch characteristics of the gas mixture. For example, adjustments in the ion concentration of the gas mixture can significantly alter its etch selectivity (e.g., SiOx:SiNx etch ratios, Poly-Si:SiOx etch ratios, etc.). It can also shift the balance of conformal-to-flowable of a deposited dielectric material.
• The plurality ofholes122 may be configured to control the passage of the activated gas (i.e., the ionic, radical, and/or neutral species) through theion suppressor110. For example, the aspect ratio of the holes (i.e., the hole diameter to length) and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through theion suppressor110 is reduced. The holes in theion suppressor110 may include a tapered portion that faces theplasma excitation region112, and a cylindrical portion that faces theshowerhead104. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to theshowerhead104. An adjustable electrical bias may also be applied to theion suppressor110 as an additional means to control the flow of ionic species through the suppressor.
• Theshowerhead104 is positioned between theion suppressor110 of theCCP unit102 and a gas reaction region130 (i.e., gas activation region) that makes contact with a substrate that may be mounted on apedestal150. The gases and plasma excited species may pass through theion suppressor110 into an activatedgas delivery region124 that is defined between theion suppressor110 and theshowerhead104. A portion of these gases and species may further pass thorough theshowerhead104 into agas reaction region130 that makes contact with the substrate.
• The showerhead may be a dual-zone showerhead that has a first set ofchannels126 to permit the passage of plasma excited species, and a second set of channels that deliver a second gas/precursor mixture into the gas reaction/activation region130. The two sets of channels prevent the plasma excited species and second gas/precursor mixture from combining until they reach thegas reaction region130. In some embodiments, one or more of theholes122 in theion suppressor110 may be aligned with one or more of thechannels126 in theshowerhead104 to allow at least some of the plasma excited species to pass through ahole122 and achannel126 without altering their direction of flight. In additional embodiments, the second set of channels may have an annular shape at the opening facing thegas reaction region130, and these annular openings may be concentrically aligned around the circular openings of the first set ofchannels126.
• The second set of channels in theshowerhead104 may be fluidly coupled to a source gas/precursor mixture (not shown) that is selected for the process to be performed. For example, when the processing system is configured to perform a deposition of a dielectric material such as silicon dioxide (SiO_x) the gas/precursor mixture may include a silicon-containing gas or precursor such as silane, disilane, TSA, DSA, TEOS, OMCTS, TMDSO, among other silicon-containing materials. This mixture may react ingas reaction region130 with an oxidizing gas mixture that may include plasma excited species such as plasma generated radical oxygen (O), activated molecular oxygen (O₂) and ozone (O₃), among other species. Excessive ions in the plasma excited species may be reduced as the species move through theholes122 in theion suppressor110, and reduced further as the species move through thechannels126 in theshowerhead104. In another example, when the processing system in configured to perform an etch on the substrate surface, the source gas/precursor mixture may include etchants such as oxidants, halogens, water vapor and/or carrier gases that mix in thegas reaction region130 with plasma excited species distributed from the first set of channels in theshowerhead104.
• The processing system may further include apower supply140 electrically coupled to theCCP unit102 to provide electric power to thelid106 and/orion suppressor110 to generate a plasma in theplasma excitation region112. The power supply may be configured to deliver an adjustable amount of power to theCCP unit102 depending on the process performed. In deposition processes for example, the power delivered to theCCP unit102 may be adjusted to set the conformality of the deposited layer. Deposited dielectric films are typically more flowable at lower plasma powers and shift from flowable to conformal when the plasma power is increased. For example, an argon containing plasma maintained in theplasma excitation region112 may produce a more flowable silicon oxide layer as the plasma power is decreased from about 1000 Watts to about 100 Watts or lower (e.g., about 900, 800, 700, 600, or 500 Watts or less), and a more conformal layer as the plasma power is increased from about 1000 Watts or more (e.g., about 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700 Watts or more). As the plasma power increases from low to high, the transition from a flowable to conformal deposited film may be relatively smooth and continuous or progress through relatively discrete thresholds. The plasma power (either alone or in addition to other deposition parameters) may be adjusted to select a balance between the conformal and flowable properties of the deposited film.
• The processing system may still further include apedestal150 that is operable to support and move the substrate (e.g., a wafer substrate). The distance between thepedestal150 and theshowerhead104 help define thegas reaction region130. The pedestal may be vertically or axially adjustable within theprocessing chamber100 to increase or decrease thegas reaction region130 and effect the deposition or etching of the wafer substrate by repositioning the wafer substrate with respect to the gases passed through theshowerhead104. Thepedestal150 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the wafer substrate. Circulation of the heat exchange fluid allows the substrate temperature to be maintained at relatively low temperatures (e.g., about −20° C. to about 90° C.). Exemplary heat exchange fluids include ethylene glycol and water.
• Thepedestal150 may also be configured with a heating element (such as a resistive heating element) to maintain the substrate at heating temperatures (e.g., about 90° C. to about 1100° C.). Exemplary heating elements may include a single-loop heater element embedded in the substrate support platter that makes two or more full turns in the form of parallel concentric circles. An outer portion of the heater element may run adjacent to a perimeter of the support platten, while an inner portion may run on the path of a concentric circle having a smaller radius. The wiring to the heater element may pass through the stem of the pedestal.
• FIG. 3 shows a simplified schematic300 of the gas flow paths of a pair of gas mixtures through a processing system that includes both an ion suppressor plate and a showerhead. Atblock305, a first gas, such as a plasma generating gas mixture, is supplied to the processing chamber via a gas inlet. The first gas may include one or more of the following gases: CF₄, NH₃, NF₃, Ar, He, H₂O, H₂, O₂, etc. Inside the processing chamber, the first gas may be excited through a plasma discharge to form one or more plasma effluents atblock310. Alternatively (or in addition to the in-situ plasma generation) a remote plasma system (RPS) coupled to the processing chamber may be used generate an ex-situ plasma whose plasma excitation products are introduced into the process chamber. The RPS plasma excitation products may include ionically-charged plasma species as well as neutral and radical species.
• Whether the plasma effluents are generated by an in-situ plasma unit, an RPS unit, or both, they may be passed through an ion suppressor in the processing chamber atblock315. The ion suppressor may block and/or control the passage of ionic species while allowing the passage of radical and/or neutral species as the plasma activated first gas travels to the gas reaction region in the processing chamber. Atblock320, a second gas may be introduced into the processing chamber. As noted above, the contents of the second gas depend on the process performed: For example, the second gas may include deposition compounds (e.g., Si-containing compounds) for deposition processes and etchants for etch processes. Contact and reaction between the first and second gases may be prevented until the gases arrive at the gas reaction region of the process chamber.
• One way to prevent the first and second gases from interacting before the gas reaction region is to have them flow though separate channels in a dual-zone showerhead.Block330 shows the activated first gas and second gas passing through a DZSH that has a first plurality of channels that permit the activated first gas to pass through the showerhead without interacting with the second gas that passes through a second plurality of channels. After exiting the DZSH, the first and second gases may mix together in the gas reaction region of the processing chamber atblock335. Depending on the process performed, the combined gases may react to deposit a material on the exposed surfaces of the substrate, etch materials from the substrate, or both.
• Referring now toFIG. 4, a simplified cross-sectional view of aprocessing system400 having ashowerhead402 that also acts as an ion suppression element is shown. In the configuration shown, a first gas source forplasma generation402 is fluidly coupled to anoptional RPS unit404 where a first plasma may be generated and the plasma effluents transported into theprocessing chamber406 throughgas inlet408. Inside theprocessing chamber406, the gases may pass throughholes410 in agas distribution plate412 into agas region414 defined between theplate412 andshowerhead402. In some embodiments, thisregion414 may be a plasma excitation/activation region where thegas distribution plate412 andshowerhead402 act as first and second electrodes to further excite the gas and/or generate the first plasma. Theholes410 in thegas distribution plate412 may be dimensionally or geometrically structured to deactivate backstreaming plasma. Theplate412 andshowerhead402 may be coupled with aRF power generator422 that supplies a charge to theplate412 and showerhead402 to excite the gases and/or generate a plasma. In one embodiment, theshowerhead402 is grounded while a charge is applied toplate412.
• The excited gases or activated gases in thegas region414 may pass throughshowerhead402 into agas reaction region416 adjacent asubstrate418 to etch material from the surface of the substrate and/or deposit material on the substrate's surface. Theshowerhead402 may be a dual zone showerhead (DZSH) that allows the excited gases to pass form thegas region414 into thegas reaction region416 while also allowing a second gas (i.e., precursor gas/mixture) to flow from an external source (not shown) into thegas reaction region416 via a second gas inlet (not shown). The DZSH may prevent the activated/excited gas from mixing with the second gas until the gases flow into thegas reaction region416.
• The excited gas may flow through a plurality ofholes424 in the DZSH, which may be dimensionally and/or geometrically structured to control or prevent the passage plasma (i.e., ionically charged species) while allowing the passage of activated/excited gases (i.e., reactive radical or uncharged neutral species).FIG. 7A provides exemplary embodiments of hole configurations that may be used in the DZSH. In addition to theholes424, the DZSH may include a plurality ofchannels426 through which the second gas flows. The second gas (precursor gas) may exit theshowerhead402 through one or more apertures (not shown) that are positionedadjacent holes424. The DZSH may act as both a second gas delivery system and an ion suppression element.
• As described above, the mixed gases may deposit a material on and/or etch the surface of thesubstrate418, which may be positioned on aplaten420. Theplaten420 may be vertically movable within theprocessing chamber406. The processing of thesubstrate418 within theprocessing chamber406 may be affected by the configurations of theholes424, the pressure within thegas region414, and/or the position of thesubstrate418 within the processing chamber. Further, the configuration of theholes424 and/or pressure within thegas region414 may control the amount of ion species (plasma) allowed to pass into thegas excitation region416. The ionic concentration of the gas mixture can shift the balance of conformal-to-flowable of a deposited dielectric material in addition to altering the etch selectivity.
• Referring now toFIG. 5, a simplified cross-sectional view of anotherprocessing system500 having a plate512 (i.e., ion suppressor plate) that acts as an ion suppression element is shown. In the configuration shown, afirst gas source502 is fluidly coupled to anRPS unit504 where a first plasma may be generated and the plasma effluents transported into theprocessing chamber506 throughgas inlet508. The plasma effluents may be transported to agas region514 defined between theion suppressor plate512 and thegas inlet508. Inside thegas region514, the gases may pass throughholes510 in theion suppressor512 into a gas reaction/activation region516 defined between theion suppressor512 and a substrate528. Thesubstrate518 may be supported on aplaten520 as described above so that the substrate is movable within theprocessing chamber506.
• Also as described above, theholes510 may be dimensionally and/or geometrically structured so that the passage of ionically charged species (i.e., plasma) is prevented and/or controlled while the passage of uncharged neutral or radical species (i.e., activated gas) is permitted. The passage of ionic species may be controllable by varying the pressure of the plasma withingas region514. The pressure ingas region514 may be controlled by controlling the amount of gas delivered throughgas inlet508. The precursor gas (i.e., second gas) may be introduced into theprocessing chamber506 at one moresecond gas inlets522 positioned vertically below or parallel withion suppressor512. Thesecond gas inlet522 may include one or more apertures, tubes, etc. (not shown) in theprocessing chamber506 walls and may further include one or more gas distribution channels (not shown) to deliver the precursor gas to the apertures, tubes, etc. In one embodiment, theion suppressor512 includes one or more second gas inlets, throughwhich the precursor gas flows. The second gas inlets of theion suppressor512 may deliver the precursor gas into thegas reaction region516. In such an embodiment, theion suppressor512 functions as both an ion suppressor and a dual zone showerhead as described previously. The activated gas that passes through theholes510 and the precursor gas introduced in theprocessing chamber506 may be mixed in thegas reaction chamber516 for etching and/or deposition processes.
• Having now described exemplary embodiments of processing chambers, attention is now directed to exemplary embodiments of ion suppressors, such asion suppressor plates412 and512 andshowerhead402.
• Exemplary Ion Suppressors
• FIG. 6A shows a simplified perspective view of an ion-suppression element600 (ion suppressor) according to embodiments of the invention. The ion suppression element600 may correspond with the ion suppressor plates ofFIGS. 4 and/or5. The perspective view shows the top of the ion suppression element or plate600. The ion suppression plate600 may be generally circular shaped and may include a plurality ofplasma effluent passageways602, where each of thepassageways602 includes one or more through holes that allow passage of the plasma effluents from a first region (e.g., plasma region) to a second region (e.g., gas reaction region or showerhead). In one embodiment, the through holes of thepassageway602 may be arranged to form one or more circular patterns, although other configurations are possible. As described previously, the through holes may be geometrically or dimensionally configured to control or prevent the passage of ion species while allowing the passage or uncharged neutral or radical species. The through holes may have a larger inner diameter toward the top surface of the ion suppression plate600 and a smaller inner diameter toward the bottom surface of the ion suppression plate. Further, the through holes may be generally cylindrical, conical, or any combination thereof. Exemplary embodiments of the configurations of the through holes are provided inFIGS. 7A-B.
• The plurality of passageways may be distributed substantially evenly over the surface of the ion suppression plate600, which may provide even passage of neutral or radical species through the ion suppression plate600 into the second region. In some embodiments, such as the embodiment ofFIG. 5, the processing chamber may only include an ion suppression plate600, while in other embodiments, the processing chamber may include both a ion suppression plate600 and a showerhead, such as the showerhead ofFIG. 6B, or the processing chamber may include a single plate that acts as both a dual zone showerhead and an ion suppression plate.
• FIG. 6B shows a simplified bottom view perspective of ashowerhead620 according to embodiments of the invention. Theshowerhead620 may correspond with the showerhead illustrated inFIG. 4. As described previously, theshowerhead620 may be positioned vertically adjacent to and above a gas reaction region. Similar to ion suppression plate600, theshowerhead620 may be generally circular shaped and may include a plurality offirst holes622 and a plurality ofsecond holes624. The plurality offirst holes622 may allow plasma effluents to pass through theshowerhead620 into a gas reaction region, while the plurality ofsecond holes624 allows a precursor gas, such as a silicon precursor, etchants etc., to pass into the gas reaction region.
• The plurality offirst holes622 may be through holes that extend from the top surface of theshowerhead620 through the showerhead. In one embodiment, each of the plurality offirst holes622 may have a smaller inner diameter (ID) toward the top surface of theshowerhead620 and a larger ID toward the bottom surface. In addition, the bottom edge of the plurality offirst holes622 may be chamfered626 to help evenly distribute the plasma effluents in the gas reaction region as the plasma effluents exit the showerhead and thereby promote even mixing of the plasma effluents and precursor gases. The smaller ID of thefirst holes622 may be between about 0.5 mm and about 20 mm. In one embodiment, the smaller ID may be between about 1 mm and 6 mm. The cross sectional shape of thefirst holes622 may be generally cylindrical, conical, or any combination thereof. Further, thefirst holes622 may be concentrically aligned with the through holes ofpassageways602, when both and ion suppression element600 and ashowerhead620 are used in a processing chamber. The concentric alignment may facilitate passage of an activated gas through both the ion suppression element600 andshowerhead620 in the processing chamber.
• In another embodiment, the plurality of first holes may622 be through holes that extend from the top surface of theshowerhead620 through the showerhead, where each of thefirst holes622 have a larger ID toward the top surface of the showerhead and a smaller ID toward the bottom surface of the showerhead. Further, thefirst holes622 may include a taper region that transition between the larger and smaller IDs. Such a configuration may prevent or regulate the passage of a plasma through the through holes while permitting the passage of an activated gas. Such embodiments may be used in place or in addition to ion suppression element600. Exemplary embodiments of such through holes are provided inFIG. 7A.
• The number of the plurality offirst holes622 may be between about 60 and about 2000. The plurality offirst holes622 may also have a variety of shapes, but are generally round. In embodiments where the processing chamber includes both a ion suppression plate600 and ashowerhead620, the plurality offirst holes622 may be substantially aligned with thepassageways602 to facilitate passage of the plasma effluents through the ion suppression plate and showerhead.
• The plurality ofsecond holes624 may extend partially through the showerhead from the bottom surface of theshowerhead620 partially through the showerhead. The plurality of second holes may be coupled with or connected to a plurality of channels (not shown) that deliver the precursor gas (e.g., deposition compounds, etchants, etc.) to thesecond holes624 from an external gas source (not shown). The second holes may include a smaller ID at the bottom surface of theshowerhead620 and a larger ID in the interior of the showerhead. The number ofsecond holes624 may be between about 100 and about 5000 or between about 500 and about 2000 in different embodiments. The diameter of the second hole's smaller ID (i.e., the diameter of the hole at the bottom surface) may be between about 0.1 mm and about 2 mm. Thesecond holes624 are generally round and may likewise be cylindrical, conical, or any combination thereof. Both the first and second holes may be evenly distributed over the bottom surface of theshowerhead620 to promote even mixing of the plasma effluents and precursor gases.
• With reference toFIG. 7A, exemplary embodiments of the configurations of the through holes are shown. The through holes depicted generally include a large inner diameter (ID) region toward an upper end of the hole and a smaller ID region toward the bottom or lower end of the hole. The smaller ID may be between about 0.2 mm and about 5 mm. Further the aspect ratio of the holes (i.e., the smaller ID to hole length) may be approximately 1 to 20. Such configurations may substantially block and/or control passage of ion species of the plasma effluent while allowing the passage of radical or neutral species. For example, varying the aspect ratio may regulate the amount of plasma that is allowed to pass through the through holes. Plasma passage may further be regulated by varying the pressure of the plasma within a region directly above the through holes.
• Referring now to specific configurations, throughhole702 may include alarge ID region704 at an upper end of the hole and asmall ID region706 at a lower end of the hole with a stepped edge between the large and small IDs. Throughhole710 may include alarge ID region712 on an upper end and alarge ID region716 on a lower end of the hole with asmall ID region714 therebetween. The transition between the large and small ID regions may be stepped or blunt to provide an abrupt transition between the regions.
• Throughhole720 may include alarge ID region722 at the upper end of the hole andsmall ID region726 at a lower end of the hole with a taperedregion724 that transitions at an angle θ between the large and small regions. Theheight728 of thesmall ID region726 may depend on theoverall height727 of the hole, the angle θ of taperedregion724, the large ID, and the small ID. In one embodiment, the taperedregion724 comprises an angle of between about 15° and about 30°, and preferably about 22°; theoverall height727 is between about4 mm and about 8 mm, and preferably about 6.35 mm; the large ID is between about 1 mm and about 4 mm, and preferably about 2.54 mm; the small ID is between about 0.2 mm and 1.2 mm, and preferably about 0.89 mm, so that theheight728 of thesmall ID region726 region is between about 1 mm and about 3 mm, and preferably about 2.1 mm.
• Throughhole730 may include afirst ID region732 at the upper end of the hole, asecond ID region734 concentrically aligned with and positioned vertically belowfirst ID region732, and athird ID region736 concentrically aligned with and positioned vertically belowsecond ID region734.First ID region732 may comprise a large ID,second ID region734 may comprise a small ID, andthird ID region736 may comprise a slightly larger ID thansecond ID region734.Third ID region736 may extend to the lower end of the hole or may be outwardly tapered to anexit ID737. The taper between thethird ID region736 and theexit ID737 may taper at an angle θ₃, which may be between about 15° and about 30°, and preferably about 22°.
• Thesecond ID region734 may include a chamfered edge that transitions from thefirst ID region732 at an angle θ₁, which may be between about 110° and about 140°. Similarly, thesecond ID region734 may include a chamfered edge that transitions into thethird ID region736 at an angle θ₂, which may also be between about 110° and about 140°. In one embodiment, the large ID offirst region732 may be between about 2.5 mm and about 7 mm, and preferably about 3.8 mm; the small ID ofsecond ID region734 may be between about 0.2 mm and about 5 mm, and preferably about 0.04 mm; the slightly larger ID ofthird ID region736 may be between about 0.75 mm and about 2 mm, and preferably about 1.1 mm; and the exit ID may be between about 2.5 mm and about 5 mm, and preferably about 3.8 mm.
• The transition (blunt, stepped, tapered, etc.) between the large ID regions and small ID regions may substantially block the passage of ion species from passing through the holes while allowing the passage or radical or neutral species. For example, referring now toFIG. 7B, shown is an enlarged illustration of throughhole720 that includes thetransition region724 between thelarge ID region722 and thesmall ID region726. The taperedregion724 may substantially preventplasma725 from penetrating through the throughhole702. For example, as theplasma725 penetrates into the throughhole720, the ion species may deactivate or ground out by contacting the walls of the taperedregion724, thereby limiting the passage of the plasma through the through hole and containing the plasma within the region above the throughhole720. The radical or neutral species, however, may pass through the throughhole720. Thus, the throughhole720 may filter theplasma720 to prevent or control the passage of unwanted species. In an exemplary embodiment, thesmall ID region726 of the through holes comprises an ID of 1 mm or smaller. To maintain a signification concentration of radical and/or neutral species penetrating through the through holes, the length of the small ID region and/or the taper angle may be controlled.
• In addition to preventing the passage of plasma, the through holes described herein may be used to regulate the passage of plasma so that a desired level of plasma is allowed to pass through the through hole. Regulating the flow of plasma through the through holes may include increasing the pressure of the plasma in the gas region above the ion suppressor plate so that a desired fraction of the plasma is able to pass through the ion suppressor without deactivating or grounding out.
• Referring now toFIG. 8, a simplified illustration of a capacitively coupled plasma (CCP) unit800 is shown. Specifically, the CCP unit800 shown includes atop plate802 and abottom plate804 that define aplasma generation region810 in which a plasma is contained. As previously described, the plasma may be generated by an RPS (not shown) and delivered to theplasma generation region810 via throughhole806. Alternatively or additionally, the plasma may be generated in the CCP unit800, for example, by utilizingtop plate802 andbottom plate804 as first and second electrodes coupled to a power generation unit (not shown).
• Thetop plate802 may include a throughhole806 that allows process gas and/or plasma to be delivered into theplasma generation region810 while preventing backstreaming of plasma through thetop plate802. The throughhole806 may be configured similar to throughhole730 having first, second, and third ID regions (820,822, and824 respectively), with a chamfered edge between adjacent regions (828 and829) and atapered region826 transitioning betweenthird ID region824 and an exit ID. The taperedregion826 betweenthird ID region824 and the exit ID and/or the chamfered edge between second and third ID regions (822 and824 respectively) may prevent backstreaming of plasma by deactivating or grounding ion species as the plasma penetrates into the throughhole806.
• Similarly, thebottom plate804 may include a throughhole808 that allows the radical or neutral species to pass through the through hole while preventing or controlling the passage of ion species. The throughhole808 may be configured similar to throughhole720 having alarge ID region830, asmall ID region832, and atapered region834 that transitions between thelarge ID region830 and thesmall ID region832. The taperedregion834 may prevent the flow of plasma through the throughhole808 by deactivating or grounding ion species as previously explained while allowing radical or neutral species to pass therethrough.
• To further prevent passage of the plasma through the through holes,802 and/or804, thetop plate802 and/orbottom plate804 may receive a charge to electrically bias the plasma and contain the plasma withinplasma generation region810 and/or adjust an ion concentration in the activated gas that passes through the bottom plate. Usingtop plate802 andbottom plate804 in CCP unit800, the plasma may be substantially generated and/or maintained in theplasma generation region810, while radical and neutral species are delivered to a gas reaction region to be mixed with one or more precursor gases to etch material from or deposit material on a substrate surface.
• Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.
• Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
• As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the electrode opening” includes reference to one or more electrode openings and equivalents thereof known to those skilled in the art, and so forth.
• Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

Claims (14)

1. A substrate processing system comprising:

a capacitively coupled plasma (CCP) unit positioned inside a process chamber, wherein the CCP unit comprises a plasma excitation region formed between a first electrode and a second electrode, and wherein the first electrode comprises a first plurality of openings to permit a first gas to enter the plasma excitation region, and the second electrode comprises a second plurality of openings to permit an activated gas to exit the plasma excitation region;

a gas inlet for supplying the first gas to the first electrode of the CCP unit; and

a pedestal that is operable to support a substrate, wherein the pedestal is positioned below a gas reaction region into which the activated gas travels from the CCP unit.

2. The system ofclaim 1, wherein the system further comprises a showerhead positioned between the second electrode of the CCP unit and the gas reaction region above the pedestal, wherein the showerhead comprises a first plurality of showerhead channels that permit passage of the activated gas to the gas reaction region, and a second plurality of channels that permit passage of a second gas to the gas reaction region.

3. The system ofclaim 2, wherein the second plurality of openings in the second electrode are concentrically aligned with the first plurality of showerhead channels.

4. The system ofclaim 1, wherein the system further comprises one or more second gas inlets positioned between the second electrode and the pedestal, wherein the second gas inlets supply a second gas to the gas reaction region.

5. The system ofclaim 1, wherein the system further comprises a remote plasma system coupled to the gas inlet and operable to excite the first gas entering the process chamber through the gas inlet.

6. The system ofclaim 1, wherein the activated gas comprises at least one reactive radical.

7. A substrate processing system comprising:

a gas inlet for supplying a first gas to a processing chamber;

an electrode comprising a plurality of openings;

a showerhead comprising a first plurality of channels that permit the passage of an activated gas to a gas reaction region in the processing chamber, and a second plurality of channels that permit passage of a second gas to the gas reaction region, wherein the activated gas is formed in a plasma excitation region between the electrode and the showerhead, which also acts as a second electrode; and

a pedestal that is operable to support a substrate, wherein the pedestal is positioned below the gas reaction region.

8. The system ofclaim 7, wherein the first plurality of channels in the showerhead suppresses plasma in the plasma excitation region from entering the gas reaction region, while permitting the activated gas to pass through the showerhead.

9. The system ofclaim 7, wherein the system further comprises a one or more second gas inlets positioned between the showerhead and the pedestal, wherein the second gas inlets supply a second gas to the gas reaction region.

10. The system ofclaim 7, wherein the system further comprises a remote plasma system coupled to the gas inlet and operable to excite the first gas entering the process chamber through the gas inlet.

11. A substrate processing system comprising:

a gas inlet for supplying a first gas to a processing chamber;

an electrode comprising a first plurality of openings;

an ion suppressor comprising an electrically conductive plate having a second plurality of openings that permit the passage of an activated gas to a gas reaction region in the processing chamber, wherein the activated gas is formed in a plasma excitation region between the electrode and the ion suppressor; and

a pedestal that is operable to support a substrate, wherein the pedestal is positioned below the gas reaction region.

12. The system ofclaim 11, wherein the system further comprises a showerhead positioned between the ion suppressor and the pedestal.

13. The system ofclaim 11, wherein the system further comprises a remote plasma system coupled to the gas inlet and operable to excite the first gas entering the process chamber through the gas inlet.

14. The system ofclaim 11, wherein the system comprises an electrical power supply coupled to the electrode and the ion suppressor, wherein the power supply is operable to create an adjustable bias voltage in the ion suppressor to adjust an ion concentration in the activated gas passing from the plasma excitation region to the gas reaction region

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