Process chamber with inner support

An improved chemical vapor deposition reaction chamber having an internal support plate to enable reduced pressure processing. The chamber has a vertical-lateral lenticular cross-section with a wide horizontal dimension and a shorter vertical dimension between bi-convex upper and lower walls. A central horizontal support plate is provided between two lateral side rails of the chamber. A large rounded rectangular aperture is formed in the support plate for positioning a rotatable susceptor on which a wafer is placed. The shaft of the susceptor extends downward through the aperture and through a lower tube depending from the chamber. The support plate segregates the reaction chamber into an upper region and a lower region, with purge gas being introduced through the lower tube into the lower region to prevent unwanted deposition therein. A temperature compensation ring is provided surrounding the susceptor and supported by fingers connected to the support plate. The temperature compensation ring may be circular or may be built out to conform to the rounded rectangular shape of the support plate aperture. The ring may extend farther downstream from the susceptor than upstream. A separate sacrificial quartz plate may be provided between the circular temperature compensation ring and the rounded rectangular aperture. The quartz plate may have a horizontal portion and a vertical lip in close abutment with the aperture to prevent devitrification of the support plate. A gas injector abuts an inlet flange of the chamber and injects process gas into the upper region and purge gas into the lower region. The gas injector includes a plurality of independently controlled channels disposed laterally across the chamber, the channels merging at an outlet of the injector to allow mixing of the adjacent longitudinal edges of the separate flows well before reaching the wafer.

 

What is claimed is:

1. A reduced pressure chamber able to withstand external forces on the chamber which occur when the exterior pressure is greater than the chamber interior pressure comprising:

a quartz wall;

a quartz lower wall spaced from the upper wall, each wall having a convex outer surface and a concave interior surface;

side rails joining side edges of said walls creating a chamber space within said walls, said chamber space having a maximum interior height which is less than a maximum interior width; and

a support within the chamber fixed to and extending between said rails to resist outward deformation of said rails and flattening deformation of said walls when the chamber is subjected to an external pressure greater than pressure within the chamber;

said walls having a generally rectangular vertical projection and said side rails being generally straight.

2. The chamber of claim 1, including an inlet flange secured to one end of each of said walls and rails and an outlet flange secured to an opposite end of each of said walls and rails.

3. The chamber of claim 1, wherein said support has an inlet section and an outlet section separated by an opening in which to position a susceptor for supporting a semiconductor wafer.

4. The chamber of claim 1, wherein said support is a plate positioned to divide said chamber into an upper region and a lower region, said support having an opening in which to position a susceptor for supporting a semiconductor wafer so that said wafer is within the upper region.

5. The chamber of claim 4, including a tube depending from said lower wall below said opening for passage of a drive shaft to rotate the susceptor.

6. The chamber of claim 4, including an inlet flange secured over a first longitudinal end and having an inlet gas flow slot open to the upper region.

7. The chamber of claim 6, including an outlet flange secured over a second longitudinal end of said chamber and having an exhaust gas flow slot open to said upper region.

8. A reduced pressure chamber able to withstand external forces on the chamber which occur when the exterior pressure is greater than the interior chamber pressure comprising:

a quartz upper wall;

a quartz lower wall spaced from the upper wall, each wall having a convex outer surface and a concave interior surface, said walls having a generally rectangular vertical projection;

generally straight side rails joining side edges of said walls creating a chamber space within said walls, said chamber space having a maximum interior height which is less than the maximum interior width;

a support plate within the chamber affixed to and extending between said rails to resist outward deformation of said rails and flattening deformation of said walls when the chamber is subjected to an external pressure greater than the pressure within the chamber, said plate being positioned to divide said chamber into an upper region and a lower region, said plate having an opening in which to position a susceptor for supporting a semiconductor wafer so that said wafer is within the upper region; and

an inlet flange secured over a first longitudinal end of the chamber and having an inlet gas flow slot open to the upper region and an outlet flange secured over a second longitudinal end of said chamber and having an exhaust gas flow slot open to said upper region;

said inlet flange including a second inlet gas flow slot open to said lower region and the outlet flange having a second exhaust gas flow slot open to the lower region, wherein the upper region defines a wafer processing zone above the support plate and the lower region defines a zone below the support plate in which no wafer processing is done.

9. A reduced pressure chamber able to withstand external forces on the chamber which occur when the exterior pressure is greater than the interior chamber pressure comprising:

a quartz upper wall;

a quartz lower wall spaced from the upper wall, each wall having a convex outer surface and a concave interior surface, said walls having a generally rectangular vertical projection;

generally straight side rails joining side edges of said walls creating a chamber space within said walls, said chamber space having a maximum interior height which is less than the maximum interior width;

a support plate within the chamber affixed to and extending between said rails to resist outward deformation of said rails and flattening deformation of said walls when the chamber is subjected to an external pressure greater than the pressure within the chamber, said plate being positioned to divide said chamber into an upper region and a lower region, said plate having an opening in which to position a susceptor for supporting a semiconductor wafer so that said wafer is within the upper region;

an outlet flange secured over a longitudinal end of said chamber and having an exhaust gas flow slot open to said upper region; and

a tube depending from said lower wall below said opening for passage of a drive shaft to rotate the susceptor, said tube being sized to provide a space surrounding the shaft for passage of purge gas into said lower region, and said outlet flange including a second slot open to said lower region for exhausting said purge gas.

10. A reduced pressure chamber able to withstand external forces on the chamber which occur when the exterior pressure is greater than the interior chamber pressure comprising:

a quartz upper wall;

a quartz lower wall spaced from the upper wall, each wall having a convex outer surface and a concave interior surface;

side rails joining side edges of said walls creating a chamber space within said walls, said chamber space having a maximum interior height which is less than the maximum interior width;

a plate within the chamber affixed to and extending between said rails to resist outward deformation of said rails and flattening deformation of said walls when the chamber is subjected to an external pressure greater than the pressure within the chamber, said plate having a generally rectangular opening;

a susceptor positioned in said opening; and

a temperature compensation ring having a circular interior edge closely surrounding the susceptor and a generally rectangular exterior edge closely positioned to the edges of said plate defining said opening.

11. The chamber of claim 10, wherein said opening has rounded corners and the exterior edge of said ring has rounded corners that mate with the rounded corners of the rectangular opening.

12. The chamber of claim 10, wherein the chamber has an inlet end and an outlet end, with said susceptor being centrally positioned between said side rails but positioned closer to the inlet edge of the opening than to the outlet edge.

13. The chamber of claim 12, wherein the circular interior edge of said ring is centrally positioned from side to side in the opening but is closer to the inlet edge of the opening than the outlet edge.

14. The chamber of claim 10, wherein said ring has a leading edge and a trailing edge and the shortest distance between the leading edge and the plate opening is less than the shortest distance between the trailing edge of the ring and the plate opening.

15. The chamber of claim 10, wherein said plate is made of quartz and said ring and said susceptor are made of graphite with a silicon carbide coating.

16. A quartz chamber for processing semiconductor wafers having a gas inlet end and a gas exhaust end, and having a longitudinal direction defined between said ends, said chamber comprising:

outwardly convex upper and lower walls;

reinforced side rails attached to lateral edges of said walls to define a generally lenticular outer shape perpendicular to said longitudinal direction with the shape having a substantially uniform cross section throughout its length between said ends, said shape having a major dimension across said side rails and a minor dimension across apexes of said upper and lower walls; and

one or more supports positioned entirely within said chamber and connected to restrict said convex walls from flattening during reduced-pressure processing within said chamber.

17. The chamber of claim 16, wherein said support is a plate attached to said side rails dividing an interior space of said chamber into an upper and a lower region.

18. The chamber of claim 17, wherein said plate is attached to said side rails at locations such that said upper and a lower regions are symmetric.

19. The chamber of claim 17, wherein said gas inlet end comprises a flange having a gas inlet slot open to said upper region which defines a wafer processing zone.

20. The chamber of claim 17, including support elements attached to said plate for supporting a ring to be positioned around the susceptor.

21. The chamber of claim 17, wherein said plate includes an aperture sized to receive a susceptor for supporting a wafer in said upper region.

22. The chamber of claim 21, including a plurality of support rods attached to said plate for supporting a temperature sensing means around the periphery of the susceptor.

23. The chamber of claim 22, wherein said temperature sensing means includes a ring housing a sensing end of a thermocouple.

24. A quartz chamber for processing semiconductor wafers having a gas inlet end and a gas exhaust end and having a longitudinal direction defined between said end, said chamber comprising:

outwardly convex upper and lower walls;

reinforced side rails attached to lateral edges of said walls to define a generally lenticular outer shape perpendicular to said longitudinal direction having a major dimension across said side rails and a minor dimension across apexes of said upper and lower walls; and

one or more supports positioned entirely within said chamber and connected to restrict said convex walls from flattening during reduced pressure processing within said chamber, said one or more supports comprising a plate attached to said side rails dividing an interior space of said chamber into an upper and at lower region, said plate being attached to said side rails at locations such that said upper and lower regions are symmetric,

each of said side rails including short laterally extending stub walls extending longitudinally from said inlet end to said exhaust end, one of each said stub walls being attached to said upper and lower walls and one being attached to said plate, each of said side rails including rounded recesses between said stub walls defining lateral boundaries of said upper and lower regions.

25. A quartz chamber for processing semiconductor wafers having a gas inlet end and a gas exhaust end, and having a longitudinal direction defined between said end, said chamber comprising:

outwardly convex upper and lower walls;

reinforced side rails attached to lateral edges of said walls to define a generally lenticular outer shape perpendicular to said longitudinal direction having a major dimension across said side rails and a minor dimension across apexes of said upper and lower walls; and

one or more supports positioned entirely within said chamber and connected to restrict said convex walls from flattening during reduced-pressure processing within said chamber, said one or more supports comprising a plate attached to said side rails dividing an interior space of said chamber into an upper and a lower region;

said gas inlet end comprising a flange having a gas inlet slot open to said lower region, wherein said lower region defines a zone below the support plate in which no wafer processing is done.

26. A quartz chamber for processing semiconductor wafers having a gas inlet end and a gas exhaust end and having a longitudinal direction defined between said ends, said chamber comprising:

outwardly convex upper and lower walls;

reinforced side rails attached to lateral edges of said walls to define a generally lenticular outer shape perpendicular to said longitudinal direction having a major dimension across said side rails and a minor dimension across apexes of said upper and lower walls; and

one or more supports positioned entirely within said chamber and connected to restrict said convex walls from flattening during reduced-pressure processing within said chamber, said one or more supports comprising a plate attached to said side rails dividing an interior space of said chamber into an upper and a lower region,

said gas exhaust end comprising a flange having a first gas exhaust slot open to said upper region and a second gas exhaust slot open to said lower region.

27. The chamber of claim 26, wherein said plate includes a plurality of support rods attached thereto extending beneath said aperture, a ring surrounding the susceptor and supported on said rods, said ring being formed to house a sensing end of a thermocouple extending into said chamber through said second gas exhaust slot.

28. A system for processing semiconductors, comprising:

a lenticular quartz chamber having a longitudinal axis;

upper and lower outwardly convex walls creating a substantially uniform cross section about said axis, and an internal central support plate positioned across said chamber and constructed to resist flattening of said walls when the chamber is subjected to an internal pressure less than external pressures;

an opening formed in said plate side to receive a susceptor for supporting a semiconductor wafer;

a tube depending from said lower wall below said opening;

a rotation shaft extending through said tube and having an upper end adapted to support said susceptor;

a plurality of radiant heating lamps positioned above and below said chamber for heating said susceptor;

a gas inlet into said chamber above said plate at one end of said chamber; and

a gas outlet from said chamber above said plate and located on the opposite side of said susceptor from said inlet.

29. The system of claim 28, comprising:

a plurality of support fingers attached to said plate and extending beneath said opening; and

a separate ring sized to fit within said opening and sized to receive and surround said susceptor, said ring being supported by said fingers.

30. The system of claim 28, wherein said chamber includes an inlet flange containing said gas inlet, and a gas injector engaging said inlet flange and including a plurality of gas inlet passages leading to said chamber inlet, and a plurality of individual metering valves controlling flow through said passages.

31. A system for processing semiconductors, comprising

a lenticular quartz chamber having upper and lower outwardly convex walls and an internal central plate positioned and constructed to resist flattening of said walls when the chamber is subjected to an internal pressure less than external pressures;

an opening formed in said plate sized to receive a susceptor for supporting a semiconductor wafer;

a tube depending from said lower wall below said opening;

a rotation shaft extending through said tube and having an upper end adapted to support said susceptor;

a plurality of radiant heating lamps positioned above and below said chamber for heating said susceptor;

a gas inlet into said chamber above said plate;

a gas outlet from said chamber above said plate and located on the opposite side of said susceptor from said inlet;

a plurality of support fingers attached to said plate and extending beneath said opening; and

a separate ring sized to fit within said opening and sized to received and surround said susceptor, said ring being supported by said fingers,

said opening being rectangular with rounded corners.

32. The system of claim 31, wherein said ring has a circular inner diameter and a rounded rectangular outer shape conforming closely with said rounded rectangular opening.

33. A system for processing semiconductors, comprising

a lenticular quartz chamber having upper and lower outwardly convex walls and an internal central plate positioned and constructed to resist flattening of said walls when the chamber is subjected to an internal pressure less than external pressures;

an opening formed in said plate sized to receive a susceptor for supporting a semiconductor wafer;

a tube depending from said lower wall below said opening;

a rotation shaft extending through said tube and having an upper end adapted to support said susceptor;

a plurality of radiant heating lamps positioned above and below said chamber creating said susceptor;

a gas inlet into said chamber above said plate;

a gas outlet from said chamber above said plate and located on the opposite side of said susceptor from said inlet; and

a purge gas inlet into said chamber below said plate and a purge gas outlet from said chamber below said plate.

34. An apparatus for use in a chemical vapor deposition chamber comprising a temperature compensation ring having an interior edge defining a generally circular opening for receiving a susceptor adapted to support a semiconductor wafer, said ring having a generally rectangular exterior edge with rounded exterior corners to fit within a similarly sized opening in the chamber.

35. The apparatus of claim 34, wherein said ring has a leading edge and a trailing edge and a pair of exterior side edges, the shortest distance between the leading exterior edge and the interior edge is less than the shortest distance between the trailing edge and the interior edge.

36. The apparatus of claim 34, wherein said ring is made of graphite.

37. The apparatus of claim 34, including a generally circular susceptor positioned within said ring.

38. The apparatus of claim 34, wherein said ring has an inner, generally annular hollow portion adapted to receive one or more temperature sensors.

39. The apparatus of claim 38, wherein said chamber has a gas inlet on an upstream end and a gas outlet on a downstream end, and said ring has a non-hollow, generally flat leading edge portion extending upstream from said hollow portion and a non-hollow, generally flat trailing edge portion extending downstream from the hollow portion.

40. An apparatus for chemical vapor deposition, comprising:

walls defining a deposition chamber having a chamber gas inlet on an upstream end and a gas outlet on a downstream end;

a generally horizontal quartz inlet wall extending from said inlet to a downstream edge defining part of an opening for receiving a susceptor;

a generally circular susceptor horizontally positioned in said opening for receiving a semiconductor substrate for vapor deposition purposes;

a sacrificial quartz plate having a horizontal portion and a vertical lip extending into said opening closely adjacent to said inlet wall downstream edge to minimize vapor deposition on and devitrification of said downstream edge;

a portion of said opening defined by said downstream edge being curved and said vertical lip being similarly curved and sized to protect one portion of said downstream edge; and

a second sacrificial quartz plate which is a mirror image of the first mentioned sacrificial quartz plate to protect a second portion of said downstream edge.

41. An apparatus for chemical vapor deposition, comprising:

walls defining a deposition chamber having a chamber gas inlet on an upstream end and a gas outlet on a downstream end;

a generally horizontal quartz inlet wall extending from said inlet to a downstream edge defining part of an opening for receiving a susceptor;

a generally circular susceptor horizontally positioned in said opening for receiving a semiconductor substrate for vapor deposition purposes;

a sacrificial quartz plate having a horizontal portion and a vertical lip extending into said opening closely adjacent to said inlet wall downstream edge to minimize vapor deposition on and devitrification of said downstream edge; and

said sacrificial plate being supported beneath that wall and its vertical lip extending upwardly adjacent the downstream edge of said inlet wall.

42. An apparatus for chemical vapor deposition, comprising:

walls defining a deposition chamber having a chamber gas inlet on an upstream end and a gas outlet on a downstream end;

a generally horizontal quartz inlet wall extending from said inlet to a downstream edge defining part of an opening for receiving a susceptor;

a generally circular susceptor horizontally positioned in said opening for receiving a semiconductor substrate for vapor deposition purposes;

a sacrificial quartz plate having a horizontal portion and a vertical lip extending into said opening closely adjacent to said inlet wall downstream edge to minimize vapor deposition; and

the horizontal portion of said sacrificial plate being in the form of a tray that extends beneath the susceptor and having a central hole for receiving a shaft rotatably supporting the susceptor.

43. An apparatus for chemical vapor deposition, comprising:

walls defining a deposition chamber having a chamber gas inlet on an upstream end and a gas outlet on a downstream end;

a generally horizontal quartz inlet wall extending from said inlet to a downstream edge defining part of an opening for receiving a susceptor;

a generally circular susceptor horizontally positioned in said opening for receiving a semiconductor substrate for vapor deposition purposes;

a sacrificial quartz plate having a horizontal portion and a vertical lip extending into said opening closely adjacent to said inlet wall downstream edge to minimize vapor deposition on and devitrification of said downstream edge; and

a temperature compensation ring in said opening surrounding the susceptor with a slight gap between the exterior of the ring and the downstream edge of the inlet wall forming said opening, said sacrificial plate vertical lip extending into said gap.

44. The apparatus of claim 43, wherein the horizontal portion of the quartz plate rests on said horizontal wall.

45. The apparatus of claim 43, herein said inlet wall downstream edge includes a generally straight central portion with concave curved edge portions, said ring has a generally rectangular exterior edge with an upstream portion that conforms to the shape of said inlet wall downstream edge, said sacrificial plate vertical lip being formed to conform to the shape of said downstream edge of the inlet wall and the upstream edge of said ring.

46. The apparatus of claim 43, wherein said sacrificial plate is positioned beneath said ring with its vertical lip extending upwardly into the gap between the ring and the downstream edge of the inlet wall, and the sacrificial plate further including a horizontal flange extending from the upper edge of the vertical wall and upstream over a portion of said inlet wall.

47. The apparatus of claim 43, including a generally horizontal quartz outlet wall extending downstream from said temperature compensation ring towards said gas outlet, and an upstream end of the tray is supported beneath the downstream edge of said inlet wall, and a downstream edge of said tray is supported beneath said outlet wall.

48. An apparatus for chemical vapor deposition, comprising:

walls defining a deposition chamber having a chamber gas inlet on an upstream end and a gas outlet on a downstream end;

a generally horizontal quartz inlet wall extending from said inlet to a downstream edge defining part of an opening for receiving a susceptor;

a generally horizontal quartz outlet wall extending from said outlet to an upstream edge defining part of said opening for receiving said susceptor;

a generally circular susceptor horizontally positioned in said opening for receiving a semiconductor substrate for vapor deposition purposes;

a sacrificial quartz plate surrounding the susceptor and positioned adjacent both the downstream and upstream edges, the opening having a rounded rectangular shape and the plate having an outer shape which closely conforms to the opening with a minimum of clearance therebetween.

49. An apparatus for processing semiconductor substrates, comprising:

a pair of curved walls each having a convex exterior surface and a concave interior surface with the concave surfaces facing each other;

connector walls joining edges of said curved walls to create an interior space;

an inlet for inserting a substrate into said space; and

a generally rectangular plate extending between and affixed to said connector walls to resist flattening deformation of said curved walls when the inlet is closed and the curved walls are subjected to an external pressure greater than pressure within the space, said plate dividing the space into an upper region and an lower region and having a hole in it sized to receive a support for the substrate.

FIELD OF THE INVENTION

This invention relates to process chambers for chemical vapor deposition or other processing of semiconductor wafers and the like. More particularly, the invention relates to a process chamber capable of withstanding stresses associated with high temperature, low pressure processes, and having improved wafer temperature uniformity and gas flow characteristics.

BACKGROUND OF THE INVENTION

Process chambers for thermally processing semiconductor wafers are desirably made of quartz (vitreous silica) or similar material because quartz is substantially transparent to radiant energy. Thus, radiant heaters may be positioned adjacent the exterior of the chamber, and a wafer being processed in the chamber can be heated to elevated temperatures without having the chamber walls heated to the same level. On the other hand, quartz is desirable because it can withstand very high temperatures. Quartz is also desirable because of its inert characteristics that enable it to withstand degradation by various processing gases and because of its high purity characteristics.

For applications in which the pressure within a quartz chamber is to be reduced much lower than the surrounding ambient pressure, cylindrical or spherical chambers are preferred from a strength standpoint because their curved surfaces can best withstand the inwardly directed force. However, when positioning a flat wafer for chemical vapor deposition purposes where the deposition gases flow parallel to the wafer, it is desirable that the chamber wall be parallel to the facing flat surface of the wafer, to obtain even deposition on the wafer surface. Uniform deposition is critical to obtain a high yield of acceptable products to be made from such wafer. However, a flat wall will collapse inwardly with reduced interior pressure sooner than will an outwardly convex wall of similar size and thickness.

To handle the inwardly directed forces oil flat wall chambers, gussets have been provided on the exterior of the walls extending generally perpendicular to the walls to which they are joined, as may be seen in U.S. Pat. No. 4,920,918. That patent also illustrates gussets on the exterior of a chamber having upper and lower outwardly convex elliptical walls having a large radius of curvature, thus providing a somewhat flattened, but curved, configuration. This compromise provides some additional strength from the curved walls while not affecting the evenness of deposition appreciably. One significant disadvantage of such design is that the external gussets complicate and interfere with the external positioning of radiant heat lamps. Furthermore, the complexity and mass of the quartz gussets increases material and fabrication expense.

Of course, flat walls can be made thicker to increase strength, but that adds cost and adversely affects heating and cooling characteristics of the chamber.

U.S. Pat. No. 5,085,887 discloses a chamber which includes a circular, slightly domed, or curved upper chamber wall to accommodate the load of reduced chamber pressure. The circular wall is provided with a greatly thickened peripheral flange that radially confines the upper wall to cause the domed wall to bow outward due to thermal expansion, helping to resist the exterior ambient pressure in vacuum applications. The chamber requires a complex mechanism for clamping the thickened exterior flanges of the upper and lower chamber walls.

Due to the high temperatures associated with thermally activated chemical vapor deposition processes, the walls of the process chamber often heat up to a certain degree, and chemical particulates are deposited thereon. These particulates can cause serious problems with the purity of the resulting processed wafer. As a result, there has been a large effort to reduce the buildup of particulate matter on reaction chamber walls. One solution is to periodically etch the insides of the process chambers to remove the particulate matter before it accumulates to a harmful level. Unfortunately, quartz process chambers take a long time to heat up due to their high transparency to radiant heat. These periodic slow etch cycles thus reduce the maximum throughput of the machine.

There has also been attempts at controlling the gas flow profile in parallel across the wafer to be processed so as to create a more uniform deposition. For example, U.S. Pat. No. 5,221,556 discloses a system in which the apertures through a gas inlet manifold are varied in size to allow more gas through one section, typically the center section, as opposed to others. U.S. Pat. No. 5,269,847 includes valves for adjustment of pairs of gas flows merging into a number of independent streams distributed laterally upstream of the wafer to be processed. This system emphasizes the importance of channeling the various gas flows separately until just before the wafer leading edge so as to prevent premature mixing and enable greater control over the flow and concentration profiles of reactant and carrier gases across the wafer.

Another problem which has not been sufficiently addressed in the prior art is that of recirculation of the process gas in parallel flow reactors. More particularly, after the gas travels in parallel over the wafer and susceptor, it may experience temperature gradients between the hot susceptor and cooler chamber walls. This can lead to recirculations as the gas rises toward the walls and is subsequently cooled. Also, the gas flow may be constricted proximate an exhaust conduit which may create turbulence and recirculations. Recirculations from either source may migrate upstream to impact the uniformity of flow in the area of the wafer thus reducing the uniformity of film deposition.

Additionally, the temperature gradient across the wafer is nonuniform from the leading edge to the trailing edge. That is, the temperature of the gas is primarily determined by its proximity to the heat-absorbing susceptor underneath the wafer. As the gas approaches and passes over the susceptor, it heats up fairly quickly to a maximum temperature towards the downstream edge of the susceptor, and then drops off after traveling past that point. This temperature nonuniformity may further negatively affect film deposition uniformity.

A need exists for an improved chamber for chemical vapor deposition purposes, and other high temperature processes, that can be made of quartz or similar materials and yet withstand the stresses incident to reduced pressure processes. There is also a need for a more uniform temperature and flow environment surrounding the wafer to ensure more uniform deposition thereof. Also, a more responsive flow control system is needed. Finally, there is a need for a more energy efficient chemical vapor deposition system with higher throughput.

SUMMARY OF THE INVENTION

Briefly stated, the invention provides a process chamber having thin upper and lower curved walls forming a flattened configuration. The upper and lower curved walls have a convex exterior surface and a concave interior surface. These walls are joined at their side edges to side rails, thus giving the chamber a generally flattened ellipsoidal or lenticular cross section, wherein the internal height of the chamber is less than the width or distance between the side walls. An internal support extending across and joined to the side rails provides the strength necessary to prevent collapse of the chamber when operating in a mode in which the interior of the chamber is at a pressure lower than that outside the chamber.

In a preferred form, the chamber upper and lower walls are generally rectangular in shape, and the spaced side rails extend the length of the walls. This produces an elongated configuration. The internal support is in the form of a plate that includes an inlet section extending to an inlet flange and an outlet section extending to an outlet flange, with a large opening between the two sections. The support plate essentially divides the chamber into an upper and lower region. A susceptor is positioned in the opening in the plate, and is supported on a shaft that extends through a tube depending from the lower wall of the chamber. A semiconductor wafer or other element to be processed can be inserted through the inlet flange and supported on the susceptor approximately aligned with the inlet section of the support plate so that processing gases may flow smoothly over the inlet support plate section and across the surface of the wafer to be processed. In this respect, the upper region of the chamber is preferably exclusively assigned to the task of wafer processing.

The chamber upper and lower walls are preferably made of quartz and are constructed by cutting segments from a large diameter cylindrical tube, or otherwise formed into curvilinear plates. These segments are welded to sidewalls which may be molded or cut to shapes to facilitate welding to the edges of the upper and lower walls. It is also possible, but not preferred, to build this structure with elements having elliptical, parabolic, or slumped plate cross sections, which are not well defined by simple circular, elliptical, or parabolic geometries.

The support plate is also preferably made of quartz and located centered between the upper and lower walls so that the stress on those walls is uniform.

The chamber disclosed thus has the advantages of being able to withstand reduced pressure processing, being made into an integral unit, and not requiring external support elements that interfere with the positioning of radiant heaters for transmitting radiant energy through the thin quartz upper and lower walls. Also, the internal support plate does not interfere with the flow of process gases through the chamber; and in fact, assists in providing the desired gas flow by conducting greater gas flow at the center of the flow path than at the edges. Further, the internal support does not interfere with the insertion or removal from the chamber of wafers, susceptors, or susceptor rings.

In a still further aspect of the present invention, an apparatus for chemical vapor deposition is provided which comprises walls defining a deposition chamber having a chamber gas inlet and outlet. A generally horizontal quartz inlet wall extends from the inlet of the chamber to a downstream edge defining part of an opening for receiving a susceptor. A generally circular susceptor is horizontally positioned in the opening and receives a semiconductor substrate for vapor deposition purposes. The apparatus further includes a sacrificial quartz plate having a horizontal portion and a vertical lip extending into the opening closely adjacent to the downstream edge of the inlet wall to minimize vapor deposition on and devitrification of the downstream edge. In a particular embodiment, the horizontal portion of the quartz plate rests on the inlet wall. The portion of the opening defined by the downstream edge is curved and the vertical lip may be curved to conform to the curved portion of the opening and is sized to protect one half of the downstream edge of the inlet wall. A second sacrificial plate may be provided having a vertical lip curved to conform to a curved edge of the susceptor or a ring positioned around the susceptor to protect a second half of the downstream edge.

In one particular embodiment the sacrificial plate is supported beneath the inlet wall, and its vertical lip extends upward adjacent the downstream edge of the inlet wall. The sacrificial plate may be in the form of a tray that extends beneath the susceptor and has a central hole for receiving a shaft rotatably supporting the susceptor. The apparatus may include a generally horizontal quartz outlet wall extending downstream from the susceptor and spaced therefrom, whereby an inlet end of the tray is supported beneath the inlet wall and a downstream edge of the tray is supported beneath the outlet wall.

In another aspect, the present invention provides a method of using a chemical vapor deposition chamber, the chamber having a quartz horizontal inlet wall with a downstream edge defining a portion of an opening in which a horizontally extending susceptor is positioned, adapted to receive a substrate. The method includes positioning a vertical lip of a sacrificial quartz plate between the downstream edge of the inlet wall and the susceptor to minimize the vapor deposition on and the devitrification of the downstream edge of the inlet wall. A temperature compensation ring surrounding the susceptor and extending between the susceptor and the downstream edge of the inlet wall may be provided. A vertical lip of the sacrificial plate is preferably positioned in a gap between the temperature compensation ring and the downstream edge of the inlet wall. The method may include pro