US20070107661A1 - Methods, systems, and apparatus for uniform chemical-vapor depositions - Google Patents

Abstract

Integrated circuits, the key components in thousands of electronic and computer products, are generally built layer by layer on a silicon substrate. One common technique for forming layers is called chemical-vapor deposition (CVD.) Conventional CVD systems not only form layers that have non-uniform thickness, but also have large chambers that make the CVD process wasteful and slow. Accordingly, the inventor devised new CVD systems, methods, and apparatuses. One exemplary CVD system includes an outer chamber, a substrate holder, and a unique gas-distribution fixture. The fixture includes a gas-distribution surface having holes for dispensing a gas and a gas-confinement member that engages or cooperates with the substrate holder to form an inner chamber within the outer chamber. The inner chamber has a smaller volume than the outer chamber, which not only facilitates depositions of more uniform thickness, but also saves gas and speeds up the deposition process.

Description

• This application is a Divisional of U.S. application Ser. No. 10/931,845, filed Aug. 31, 2004, which is a Divisional of U.S. application Ser. No. 09/797,324, filed Mar. 1, 2001, now U.S. Pat. No. 6,852,167, both of which are incorporated herein by reference.
TECHNICAL FIELD
• This invention concerns methods of making integrated circuits, particularly layer-formation, such as chemical-vapor deposition.
BACKGROUND OF THE INVENTION
• Integrated circuits, the key components in thousands of electronic and computer products, are interconnected networks of electrical components fabricated on a common foundation, or substrate. Fabricators generally build these circuits layer by layer, using techniques, such as deposition, doping, masking, and etching, to form thousands and even millions of microscopic resistors, transistors, and other electrical components on a silicon substrate, known as a wafer. The components are then wired, or interconnected, together to define a specific electric circuit, such as a computer memory.
• One common technique for forming layers in an integrated circuit is called chemical vapor deposition. Chemical vapor deposition generally entails placing a substrate in a reaction chamber, heating the substrate to prescribed temperatures, and introducing one or more gases, known as precursor gases, into the chamber to begin a deposition cycle. The precursor gases enter the chamber through a gas-distribution fixture, such as a gas ring or a showerhead, one or more centimeters above the substrate, and descend toward the heated substrate. The gases react with each other and/or the heated substrate, blanketing its surface with a layer of material. An exhaust system then pumps gaseous by-products or leftovers from the reaction out of the chamber through a separate outlet to complete the deposition cycle.
• Conventional chemical-vapor-deposition (CVD) systems suffer from at least two problems. First, conventional CVD systems generally form layers that include microscopic hills and valleys and thus have non-uniform thickness. In the past, fabricators have been able to overcome these hills and valleys through use of post-deposition planarization or other compensation techniques. However, escalating demands for greater circuit density, for thinner layers, and for larger substrates make it increasingly difficult, if not completely impractical, to overcome the non-uniform thickness of conventional CVD layers.
• Second, some conventional CVD systems are also inefficient and time consuming. One significant factor affecting both CVD efficiency and duration is the size of conventional reaction chambers, which are generally made large to allow a loading mechanism to insert and extract the substrate. Large chambers generally require more gases to be introduced to achieve desired gas concentrations. However, much of this gas is not only unnecessary based on the amount of material deposited, but is typically treated as waste. Moreover, large chambers also take longer to fill up or pump out, prolonging deposition cycles and thus slowing fabrication of integrated circuits.
• Accordingly, there is a need for better systems and methods of chemical-vapor deposition.
BRIEF DESCRIPTION OF THE DRAWING
• FIG. 1 is a side view of an exemplary deposition reactor according to the invention;
• FIG. 2 is a top view of an exemplary gas-distribution fixture according to the invention;
• FIG. 3 is a flowchart showing an exemplary method according to the invention; and
• FIG. 4 is a diagram of anexemplary deposition system400 incorporating a set of four deposition stations similar in structure and function tosystem100 ofFIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
• The following detailed description, which references and incorporatesFIGS. 1-4, describes and illustrates specific embodiments of the invention. These embodiments, offered not to limit but only to exemplify and teach the invention, are shown and described in sufficient detail to enable those skilled in the art to make and use the invention. Thus, where appropriate to avoid obscuring the invention, the description may omit certain information known to those of skill in the art.
• FIG. 1 shows an exemplary chemical-vapor-deposition system100 which incorporates teachings of the present invention. In particular,system100 includes achamber110, awafer holder120, a gas-distribution fixture130, agas supply system140, andexhaust pump150, and aexhaust pump160.
• More particularly,chamber110 includes respective top andbottom plates112 and114 and asidewall116. In the exemplary embodiment,chamber110 is a cylindrical structure formed of stainless steel or glass. However, other embodiments use different structures and materials.Bottom plate114 includes an opening114.1. Extending through opening114.1 is astem portion122 ofwafer holder120.
• Wafer holder120 also includes asupport platform124, one ormore heating elements126, and one ormore temperature sensors128.Support platform124 supports one or more substrates, wafers, or integrated-circuit assemblies200.Substrate200 has an exemplary width or diameter of about 30 centimeters and an exemplary thickness in the range of 850-1000 microns. (The term “substrate,” as used herein, encompasses a semiconductor wafer as well as structures having one or more insulative, conductive, or semiconductive layers and materials. Thus, for example, the term embraces silicon-on-insulator, silicon-on-sapphire, and other advanced structures.)Heating elements126 andtemperature sensors128 are used forheating substrates200 to a desired temperature.Holder120 is coupled to a power supply and temperature control circuitry (both of which are not shown.) In the exemplary embodiment,wafer holder120 is rotatable either manually or automatically and raises via manual or automatic lever mechanism (not shown). Abovewafer holder120 andsubstrate200 is gas-distribution fixture130.
• Fixture130 includes a gas-distribution member132, a surface-projection (or gas-confinement)member134, and agas inlet136. Gas inlet132 couples to gas-supply, gas-distribution channels134, and agas inlet136. In the exemplary embodiment,fixture130 has two operating positions138.1 and138.2relative support platform124. Fixture130 takes operating position138.1, before and after depositions and operating position138.2 during depositions.
• Gas-distribution member132 includes gas-distribution holes, or orifices,132.1 and gas-distribution channels132.2. Holes132.1 define a gas-distribution surface132.3. In the exemplary embodiment, holes132.1 are substantially circular with a common diameter in the range of 15-20 microns; gas-distribution channels132.2 have a common width in the range of 20-45 microns; and surface132.3 is substantially planar and parallel to supportplatform124 ofwafer holder120. However, other embodiments use other surface forms as well as shapes and sizes of holes and channels. The distribution and size of holes may also affect deposition thickness and thus might be used to assist thickness control. Holes132.1 are coupled through gas-distribution channels132.2 togas inlet136.
• Surface-projection member134 projects or extends from surface132.3 towardsupport platform124, defining a fixture cavity134.1. The exemplary embodiment forms surface-projection member134 from stainless steel as a uniform annular or circular wall or collar that projects perpendicularly fromsurface132 to define a right-cylindrical cavity. However, other embodiments formmember134 to project at other angles relative surface132.3. For example, some form the projection at an acute or obtuse angle, such as 45 or 135 degrees, and others form the projection to peripherally define an oval, ellipse, triangle, square, or any desirable regular or irregular polygon. Thus, the present invention encompasses a wide variety of projection shapes and configurations, indeed any projection shape that facilitates definition of an effective cavity or gas-confinement volume in cooperation withwafer holder120 and/orsubstrate200.
• FIG. 2, a plan view, shows further details of the exemplary embodiment of gas-distribution fixture130. In particular, the plan view shows not only exemplary circular peripheries of gas-distribution member132 and surface-projection member134, but also an exemplary distribution pattern for holes132.1 and an exemplary orthogonal arrangement of gas-distribution channels132.2. Other embodiments, however, use other hole distribution patterns and channel arrangements. For example, some embodiments include random or concentric hole patterns and various channel geometries, including concentric circles, rectangles, or other regular or irregular concentric polygons. Some embodiments may also dedicate various subsets of channels and corresponding holes to different gases.
• Gas-distribution member132 can be made in a number of ways. One exemplary method entails providing two wafers of materials, such as silicon or other passivatable, inert, or non-reactive material. One wafer is patterned and etched, for example, using conventional photolithographic or micro-electro-mechanical systems (MEMS) technology, to form a pattern holes, and the other wafer is patterned and etched to include a complementary or corresponding pattern of gas-distribution channels. (MEMS refers to the technologies of making structures and devices with micrometer dimensions.) Dry-etching techniques produce small openings and channels, while wet etching produces larger openings and channels. For further details, see, for example, M. Engelhardt, “Modern Application of Plasma Etching and Patterning in Silicon Process Technology, ” Contrib. Plasma Physics, vol. 39, no. 5, pp. 473-478(1999).
• The two wafers are then bonded together with the holes and channels in appropriate alignment using known wafer-bonding techniques. See, for example, G. Krauter et al., “Room Temperature Silicon Wafer Bonding with Ultra-Thin Polymer Films, ” Advanced Materials, vol. 9, no. 5, pp. 417-420(1997); C.E. Hunt et al., “Direct Bonding of Micromachined Silicon Wafers for Laser Diode Heat Exchanger Applications, ” J. Micromech. Microeng, vol. 1, pp. 152-156(1991); Zucker, O. et al., “Applications of oxygen plasma processing to silicon direct bonding, ” Sensors and Actuators, A. Physical, vol. 36, no. 3, pp. 227-231(1993), which are all incorporated herein by reference. See also, copending and co-assigned U.S. patent application Ser. No. 09/189,276(dockets 303.534US1 and 97-1468) entitled “Low Temperature Silicon Wafer Bond Process with Bulk Material Bond Strength, ” which was filed Nov. 10, 1998 and which is also incorporated herein by reference. The resulting bonded structure is then passivated using thermal oxidation for example.
• For an alternative fixture structure and manufacturing method that can be combined with those of the exemplary embodiment, see U.S. Pat. No. 5,595,606, entitled “Shower Head and Film Forming Apparatus Using Same, which is incorporated herein by reference. In particular, one embodiment based on this patent adds a projection or gas-confinement member to the reported showerhead structure.
• FIG. 1 also shows thatgas inlet136 couples gas-distribution fixture130 to gas-supply system140. Gas-supply system140 includes agas line142,gas sources144 and145, and mass-flow controllers146 and147. Gas line orconduit142, which includes a flexible portion142.1, passes through an opening116.1 inchamber sidewall116 to connect withgas inlet136.Gas source144 is coupled via mass-flow controller146 togas line142, andgas source147 is coupled via mass-flow controller147 togas line142. The exemplary embodiment provides computer-controlled thermal or pressure-based mass-flow controllers; however, the invention is not limited to any particular number or type of mass-flow controller, nor to any particular number or set of gas sources.
• System100 also includesvacuum pumps150 and160.Vacuum pump150 is coupled to gas-distribution fixture130 via a mass-flow controller152 andgas line142. And,vacuum pump160 is coupled to the interior ofchamber110 via aline162 and an opening114.2 inchamber bottom plate114. In the exemplary embodiment,vacuum pump160 has a greater capacity thanvacuum pump150.
• In general operation,system100 functions, via manual or automatic control, to move gas-distribution fixture130 from operating position138.1 to position138.2, to introduce reactant gases throughfixture130 ontosubstrate200, and to deposit desired matter through chemical-vapor deposition onto the substrate. After the desired matter is deposited, pump150 evacuates gases throughfixture130.
• More particularly,FIG. 3 shows aflowchart300 which illustrates an exemplary method ofoperating system100.Flowchart300 includes process blocks202-216.
• The exemplary method begins atblock302 with insertion ofsubstrate300 ontowafer holder120. Execution then proceeds to block304.
• Block304 establishes desired temperature and pressure conditions withinchamber110. In the exemplary embodiment, this entails operatingheating element126 to heatsubstrate200 to a desired temperature, and operatingvacuum pump160 to establish a desired pressure. Temperature and pressure are selected based on a number of factors, including composition of the substrate and reactant gases, as well as the desired reaction. After establishing these deposition conditions, execution continues atblock306.
• Inblock306, the system forms or closes an inner chamber aroundsubstrate200, or more precisely a portion ofsubstrate200 targeted for deposition. In the exemplary embodiment, this entails using a lever or other actuation mechanism (not shown) to move gas-distribution fixture130 from position138.1 to position138.2 or to movewafer holder120 from position138.2 to138.1. In either case, this movement places gas-distribution surface132.3 one-to-five millimeters from an upper most surface ofsubstrate200. In this exemplary position, a lower-most surface of surface-projection member134 contacts the upper surface ofsupport platform124, with the inner chamber bounded by gas-distribution surface132.3, surface-projection member134, and the upper surface ofsupport platform124.
• Other embodiments define in the inner chamber in other ways. For example, some embodiments include a surface-projection member onsupport platform124 ofwafer holder120 to define a cavity analogous in structure and/or function to cavity134.1. In these embodiments, the surface-projection member takes the form of a vertical or slanted or curved wall, that extends fromsupport platform124 and completely aroundsubstrate200, and the gas-distribution fixture omits a surface-projection member. However, some embodiments include one or more surface-projection members on the gas-distribution fixture and the on the support platform, with the projection members on the fixture mating, engaging, or otherwise cooperating with those on the support platform to define a substantially or effectively closed chamber. In other words, the inner chamber need not be completely closed, but only sufficiently closed to facilitate a desired deposition.
• After forming the inner chamber, the exemplary method continues atblock308.Block308 entails introducing one or more reactant or precursor gases into the separate chamber. To this end, the exemplary embodiment operates one or more mass-flow controllers, such ascontrollers146 and147, to transfer gases in controlled quantities and temporal sequences from gas sources, such assources144 and147, throughgas line142 andfixture130 into the separate chamber.
• Notably, the inner chamber is smaller in volume thanchamber100 and thus requires less gas and less fill time to achieve desired chemical concentrations (assuming all other factors equal.) More precisely, the exemplary embodiment provides an inner chamber with an empty volume in the range of 70 to 350 cubic centimeters, based on a 1-to-5 millimeter inner-chamber height and a fixture with a 30-centimeter diameter. Additionally, the number and arrangement of holes in the fixture as well as the placement of the holes close to the substrate, for example within five millimeters of the substrate, promote normal gas incidence and uniform distribution of gases over the targeted portion ofsubstrate200.
• Block310 entails allowing the gases to react with each other and/or the heated substrate to deposit a layer of material on targeted portions of the substrate. It is expected that the resulting layer will exhibit a highly uniform thickness across the entire substrate because of the more uniform gas distribution.
• Next, asblock312 shows, the exemplary method entails evacuating gaseous waste or by-products produced during the deposition. To this end, the exemplary embodiment, activatesvacuum pump160 to pump gaseous waste from the inner chamber through gas-distribution fixture130. In some embodiments, pumps150 and160 are operated concurrently to establish initial pressure conditions and to evacuate the inner and outer chambers after deposition.
• Inblock314, the system opens the separate chamber. In the exemplary embodiment, this entails automatically or manually moving gas-distribution fixture130 to position138.1. Other embodiments, however, move the wafer holder or both the fixture and the wafer holder. Still other embodiments may use multipart collar or gas-confinement members which are moved laterally relative the wafer holder or gas-distribution fixture to open and close an inner chamber.
• Inblock316,substrate200 is unloaded fromchamber110. Some embodiments remove the substrate manually, and others remove it using an automated wafer transport system.
• FIG. 4 shows a conceptual representation of another exemplary chemical-vapor-deposition system400 incorporating teachings of the present invention.System400 includes a rectangularouter chamber410 which encloses fourdeposition stations420,422,424, and426, loaded withrespective substrates200,202,204, and206. Although the figure omits numerous components for clarity, each deposition station is structurally and operationally analogous tosystem100 inFIG. 1. In the exemplary embodiment, two or more of the stations are operated in parallel. Additionally, other embodiments of this multi-station system arrange the stations in a cross formation, with each station confronting a respective lateral face of the chamber. Still other embodiments use different outer chamber geometries, for example cylindrical or spherical.
Conclusion
• In furtherance of the art, the inventor has presented new systems, methods, and apparatuses for chemical-vapor deposition. One exemplary system includes an outer chamber, a substrate holder, and a unique gas-distribution fixture. The fixture includes a gas-distribution surface having holes for dispensing a gas and a gas-confinement member that engages, or otherwise cooperates with the substrate holder to form an inner chamber within the outer chamber.
• Notably, the inner chamber not only consumes less gas during deposition to reduce deposition waste and cost, but also facilitates rapid filling and evacuation to reduce deposition cycle times (with all other factors being equal.) The inner chamber also places the gas-distribution fixture within several millimeters of a substrate on the substrate holder, promoting normal gas incidence across the chamber and thus uniform deposition thickness.
• To address these and other problems, the present inventor devised new systems, methods, and apparatuses for chemical-vapor deposition. One exemplary chemical-vapor deposition system includes an outer chamber, a substrate holder, and a unique gas-distribution fixture. The fixture includes a gas-distribution surface having holes for dispensing a gas and a gas-confinement member that forms a wall around the holes. In operation, the gas-confinement member engages, or otherwise cooperates with the substrate holder to form an inner chamber within the outer chamber.
• The inner chamber has a smaller volume than the outer chamber and thus consumes less gas during the deposition process than would the outer chamber used alone. Also, the smaller chamber volume allows the exhaust system to pump the chamber more quickly, thus increasing the rate of the CVD process. In addition, the exemplary showerhead is made of a material, like silicon, which can be easily passivated to reduce reaction with reactive gases, thus reducing chemical-vapor buildup in the showerhead. Also, the exemplary showerhead includes a configuration of holes that permits uniform gas flow.
• The embodiments described above are intended only to illustrate and teach one or more ways of practicing or implementing the present invention, not to restrict its breadth or scope. The actual scope of the invention, which embraces all ways of practicing or implementing the invention, is defined only by the following claims and their equivalents.

Claims (50)

1. A chemical-vapor deposition system comprising:

a first chamber for confining gases; and

a second chamber within the first chamber for at least partially containing a substrate during deposition.

2. The system ofclaim 1, wherein the first chamber is a right cylindrical chamber.

3. The system ofclaim 1, wherein the second chamber comprises a surface of a substrate-support structure.

4. The system ofclaim 3, wherein the second chamber further comprises a gas-distribution fixture for atomic-layer deposition, the fixture confronting the surface of the substrate-support structure and comprising:

a non-reactive plate including a plurality of holes; and

a wall surrounding at least a portion of the plate.

5. The system ofclaim 1, wherein the second chamber comprises one or more heating elements operable to heat the substrate, and one or more temperature sensors operable to monitor a temperature of the substrate.

6. The system ofclaim 1, wherein the second chamber is configured to move relative to a position of the substrate.

7. The system ofclaim 1, wherein the second chamber is fluidly coupled to a gas supply system.

8. The system ofclaim 7, wherein the gas supply system comprises at least one reactant gas source, and a vacuum source.

9. The system ofclaim 1, wherein the first chamber is coupled to a vacuum source.

10. A chemical-vapor deposition system comprising:

first means for confining one or more gases;

second means for confining one or more gases, the second means at least partly contained within the first means; and

third means for confining one or more gases, the third means at least partly contained within the first means.

11. The system ofclaim 10, wherein the first means comprises a right cylindrical chamber.

12. The system ofclaim 10, wherein the third means comprises a surface of a substrate-support structure.

13. The system ofclaim 10, wherein the third means comprises one or more heating elements operable to heat a substrate positioned on the substrate-support structure, and one or more temperature sensors operable to monitor a temperature of the substrate.

14. The system ofclaim 10, wherein the second means is separated from the third means by a gas distribution surface.

15. The system ofclaim 12, wherein the third means comprises a surface projection member that cooperatively interacts with the substrate-support structure to form a gas confinement volume.

16. The system ofclaim 15, wherein the surface projection member is configured to move relative to the substrate support structure.

17. The system ofclaim 10, wherein the first means is fluidly coupled to a gas supply system.

18. The system ofclaim 17, wherein the gas supply system comprises at least one reactant gas source, and a vacuum source.

19. The system ofclaim 10, wherein the first means is coupled to a vacuum source.

20. A chemical-vapor deposition system comprising:

a first chamber for confining gases;

a second chamber within the first chamber configured to at least partially contain a substrate during deposition, the second chamber further comprising:

a first plate including one or more channels configured to communicate a gas flow; and

a second plate including two or more holes configured to communicate a gas flow, wherein the first and second plates are aligned to provide a continuous gas flow path from one of the channels to the holes.

21. The system ofclaim 20, wherein at least one of the first plate and the second plate comprises silicon.

22. The system ofclaim 21 wherein the first plate and the second plate are photo lithographically patterned and etched to form the one or more channels and the two or more holes.

23. The system ofclaim 20, wherein the first plate includes a plurality of channels orthogonally configured in the first plate.

24. The system ofclaim 20, wherein the second plate comprises a hole arrangement in the second plate.

25. The system ofclaim 24, wherein the hole arrangement includes one of a random arrangement of holes, a rectangular arrangement of holes, and a concentric arrangement of holes.

26. The system ofclaim 20, wherein the second plate includes holes that range in diameter from approximately 15 microns to approximately 20 microns.

27. The system ofclaim 20, wherein first plate includes channels that range in width from approximately 20 microns to approximately 45 microns.

28. The system ofclaim 20, wherein the first plate and the second plate are fixedly aligned by bonding the first plate and the second plate.

29. The system ofclaim 28, wherein bonding the first plate and the second plate comprises passivating the bonded structure using a thermal oxidation method.

30. The system ofclaim 20, wherein the first plate comprises a gas inlet configured to fluidly communicate with the one or more channels.

31. The system ofclaim 30, further comprising a gas supply system configured to fluidly communicate with the gas inlet.

32. A chemical-vapor deposition system comprising:

a first chamber for confining gases;

a second chamber within the first chamber to at least partially contain a substrate during a deposition process, the second chamber further comprising:

a first plate including at least one channel on a surface of the first plate and a gas inlet on an opposing surface that is configured to fluidly communicate with the at least one channel; and

a second plate including at least one aperture that extends through the second plate.

33. The system ofclaim 32, wherein the first plate and the second plate sealably joined to provide a continuous flow passage that extends from the aperture to the gas inlet.

34. The system ofclaim 32, wherein at least one of the first plate and the second plate comprises a silicon substrate.

35. The system ofclaim 32, wherein the first plate and the second plate are photo lithographically patterned and etched to form the at least one channel and the at least one aperture.

36. The system ofclaim 32, wherein the first plate includes a plurality of channels, wherein the plurality of channels are orthogonally positioned in the first plate.

37. The system ofclaim 32, wherein the second plate includes a plurality of apertures, wherein the plurality of apertures comprises an aperture pattern in the second plate.

38. The system ofclaim 37, wherein the aperture pattern includes one of a random pattern of apertures, a rectangular pattern of apertures, and a concentric pattern of apertures.

39. The system ofclaim 32, wherein the second plate includes apertures that range in size from approximately 15 microns to approximately 20 microns.

40. The system ofclaim 32, wherein first plate includes channels that range in width from approximately 20 microns to approximately 45 microns.

41. A chemical-vapor deposition system comprising:

a first chamber for confining gases;

a second chamber within the first chamber configured to at least partially contain a substrate during a deposition process, the second chamber further comprising:

a first plate including a plurality of channels on a surface, and a gas inlet on an opposing surface of the first plate that is configured to fluidly communicate with the plurality of channels;

a second plate including a plurality of apertures that extend through the second plate, the first plate and the second plate being sealably joined to provide a continuous flow passage that extends from the apertures to the gas inlet.

42. The system ofclaim 41, wherein the plurality of channels comprise channels having a common width that ranges between approximately 20 microns and approximately 45 microns.

43. The system ofclaim 41, wherein the plurality of apertures comprise apertures having a common diameter that ranges between approximately 15 microns and approximately 20 microns.

44. The system ofclaim 41, wherein the plurality of apertures comprise a random arrangement of the apertures in the second plate.

45. The system ofclaim 41, wherein the plurality of apertures comprise a circular arrangement of the apertures in the second plate.

46. The system ofclaim 41, wherein the plurality of apertures comprise a rectangular arrangement of the apertures in the second plate.

47. The system ofclaim 41, wherein the plurality of channels comprise an orthogonal arrangement of the channels.

48. The system ofclaim 41, wherein the plurality of channels comprise a concentric circular arrangement of the channels.

49. The system ofclaim 41, wherein the first plate and the second plate are sealably joined by bonding the first plate and the second plate using a silicon wafer bonding method to form a bonded structure.

50. The system ofclaim 49, wherein the bonded structure comprises a passivated and bonded structure.

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