Dogbone-shaped exhaust slit tunnel for processing chamber

Abstract

A processing chamber is disclosed, the processing chamber including a chamber body. The chamber body has a first surface, a second surface opposite the first surface, a window assembly, and a base. The first and second surfaces, the window assembly, and the base define a thermal treatment region. A flow assembly is disposed adjacent to the first surface and configured to introduce processing gas into the thermal treatment region. An exhaust slit assembly is disposed adjacent to the second surface. The exhaust slit assembly has an opening that communicates with the thermal treatment region. The opening has a center and outer edges. The center and edges are defined vertically between the window assembly and the base. The outer height at the edges of the opening is at least 30% greater vertically than the center height at the center of the opening.

Description

[Background technology]

[0001] Technical Field TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate generally to equipment for semiconductor device manufacturing, and more particularly to exhaust slit tunnels in processing chambers.

[0002] 2. Description of Related Art

[0002] The production of silicon integrated circuits has placed challenging demands on manufacturing steps, increasing the number of devices while shrinking the minimum feature size on a chip. Additionally, increasing cost pressures on device manufacturers have created a need to increase throughput in semiconductor fabrication facilities. Semiconductor substrates are processed for a wide range of applications, including the fabrication of integrated and microdevices. One method of processing a substrate involves depositing a material, such as a semiconductor material or a conductive material, on the top surface of the substrate. The deposition, modification, or removal of semiconductor material on a substrate is highly dependent on the flux of purge and process gases across the surface of the substrate. During deposition processes, process gases and purge gases (e.g., inert gases) simultaneously flow into a process chamber (e.g., an epitaxial growth (EPI) chamber). As a result, semiconductor manufacturing processes require film formation and modification steps to be performed at slow or fast rates with extreme uniformity. One such process is the deposition of a film on a semiconductor substrate. In such processes, a gas mixture flows into a processing chamber and deposits or modifies an underlying layer of a substrate by combining with precursors and / or by-products within the processing chamber to form a film.

[0003]

[0003] The profile of process gas flowing through a processing chamber from the leading edge to the trailing edge of a substrate correlates with the uniformity and quality of the deposited material layer. The shape of the process gas profile can be selected to enable improved uniformity of the deposited material layer. The demand for smaller and denser devices necessitates improved control over the shape of the process gas profile. Conventional processing chambers have had difficulty meeting the demand for improved control over the profile of process gas provided across the substrate. This makes it difficult to achieve uniform thickness deposition with tight tolerances.

[0004] Therefore, there is a need for an improved apparatus for controlling process gases within a semiconductor processing chamber. Summary of the Invention

[0005]

[0005] Disclosed herein is a processing chamber including a slit valve tunnel with a variable gap opening. The processing chamber includes a chamber body. The chamber body has a first surface, a second surface opposite the first surface, a window assembly, and a base. The first surface, the second surface, the window assembly, and the base define and surround a thermal treatment region. A flow assembly is disposed adjacent to the first surface and configured to introduce processing gas into the thermal treatment region. An exhaust slit assembly is disposed adjacent to the second surface. The exhaust slit assembly has an opening exposed to the thermal treatment region. The opening has an opening center and outer edges. The opening center and opening edges are defined vertically between the window assembly and the base. The outer height at the opening edges is at least 30% greater vertically than the central height at the opening center.

[0006] In another embodiment, an exhaust slit assembly is disposed adjacent the second surface. The exhaust slit assembly has an elongated opening communicating with the heat treatment region. The elongated opening has a central opening height located at the center of the elongated opening and an outer opening height located along an outer edge of the elongated opening. The outer opening height exceeds the central opening height by at least 30% in the vertical direction.

[0007] In another embodiment, a method for thermally processing a substrate is provided. The method includes flowing a process gas into a processing chamber through a first opening and into a processing region containing the substrate. The process gas is flowed laterally across the substrate from the first opening to a second opening in the processing chamber. The second opening has a higher conductance at the outer edges of the second opening than at the center of the second opening. The substrate is heated in the presence of the process gas, and a layer of material is deposited on the heated substrate in the presence of the process gas.

[0008]

[0008] So that the above-mentioned features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above may be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, which may also admit of other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a schematic diagram of a processing system according to one or more embodiments described herein. [Figure 1B] 2 is another schematic diagram of a processing system according to one or more embodiments described herein. [Figure 1C] 1 is a schematic top view of a processing system according to one or more embodiments described herein. [Figure 2A]FIG. 2 is a schematic top view of the exhaust slit assembly of FIG. 1 according to one or more embodiments described herein. [Figure 2B] FIG. 2 is another schematic top view of the exhaust slit assembly of FIG. 1 according to one or more embodiments described herein. [Figure 3] 2C are two elevational views of the opening of the exhaust slit assembly shown in FIGS. 2A and 2B. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0015] For ease of understanding, where possible, the same reference numerals have been used to designate identical elements that are common to multiple figures. It is contemplated that elements and features of one or more embodiments may be beneficially incorporated in other embodiments.

[0011]

[0016] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to semiconductor device manufacturing equipment and methods for processing substrates in such equipment, and more particularly to an exhaust assembly for a processing chamber. The exhaust assembly has an opening shaped to uniformly distribute process gas velocities across a substrate placed in the processing chamber. The opening is given a dog-bone or dumbbell-shaped cross-sectional opening profile instead of a conventional uniform cross-sectional profile. The dog-bone or dumbbell-shaped cross-sectional opening profile has a narrow opening (i.e., gap) in the center and widens from the center to the edge. The smaller area of ​​the opening in the center allows for better flow over the substrate, thereby improving process uniformity.

[0012]

[0017] 1A shows a substrate processing system 199 that includes an epitaxial (EPI) processing chamber 100. The EPI processing chamber 100 is utilized to grow an epitaxial film on a substrate (such as substrate 150). Alternatively, the EPI processing chamber 100 can be configured to perform etching.

[0013]

[0018] The EPI processing chamber 100 includes a chamber body 108. The chamber body 108 includes a susceptor assembly 124, a lower window 120, an upper window 122, and a base plate 114. The upper window 122, the base plate 114, and the lower window 120 surround an interior space 110 of the chamber body 108. The susceptor assembly 124 is disposed within the interior space 110 of the chamber body 108.

[0014]

[0019] The EPI processing chamber 100 further includes a plurality of lamp modules 101. The lamp modules 101 include an upper lamp module 102 and a lower lamp module 104. The upper lamp module 102 may include a pyrometer passageway in which a pyrometer (such as a scanning pyrometer) measures the temperature of the substrate 150 or components of the chamber body 108.

[0015]

[0020] The upper window 122 is an optically transparent window such that radiant energy generated by the upper lamp module 102 passes through the upper window 122. In some embodiments, the upper window 122 is formed of a quartz or glass material. The upper window 122 has a dome shape and is also referred to in some embodiments as an upper dome. The outer edge of the upper window 122 forms a peripheral support. The peripheral support is disposed on the base plate 114.

[0016]

[0021] The base plate 114 may include one or more cooling channels 188. The cooling channels 188 may be configured to have a fluid flow therethrough to maintain the temperature of the base plate 114. The upper window 122 and the base plate 114 may define a processing region 129. The substrate 150 is exposed to processing gases in the processing region 129 for processing.

[0017]

[0022] A liner 154 is disposed inside the opening of the base plate 114. The liner 154 is ring-shaped. The liner 154 is configured to isolate the inner surface of the base plate 114 from the interior space 110. The liner 154 isolates the inner surface of the base plate 114 from the process gases in the interior space 110 and also protects the interior space 110 from particles or other contaminants emitted by the base plate 114. The liner 154 also serves to reduce heat conduction from the process space to the base plate 114. Reducing heat conduction improves uniform heating of the substrate 150, allowing for more uniform deposition on the substrate 150 during processing.

[0018]

[0023] The lower window 120 is disposed between the base plate 114 and the lower lamp module 104. The lower window 120 is optically transparent so that radiant energy generated by the lower lamp module 104 passes through the lower window 120. In some embodiments, the lower window 120 is formed from quartz or a glass material. The lower window 120 has a dome shape and is also referred to as a lower dome in some embodiments. The outer edge of the lower window 120 forms a peripheral support. The base plate 114 is disposed on the peripheral support of the lower window 120.

[0019]

[0024] The lower lamp module 104 is disposed below the susceptor assembly 124 and is configured to heat the bottom surface of the substrate 150 when the substrate is placed on the susceptor assembly 124. The lower lamp module 104 includes a plurality of lamp apertures. A lamp 135 is disposed within each of the plurality of lamp apertures. Each lamp 135 is electrically coupled to a power supply (not shown). The lamps 135 are oriented generally parallel to the vertical centerline of the EPI processing chamber 100. For example, the lamps 135 can be oriented generally perpendicular to the substrate 150. Alternatively, the lamps 135 are oriented parallel to the substrate 150.

[0020]

[0025] The lower lamp module 104 further includes a susceptor shaft passage 195. The susceptor shaft passage 195 is disposed through the center of the lower lamp module 104. The support shaft 132 is disposed through the susceptor shaft passage 195 and is coupled to the susceptor assembly 124. The susceptor shaft passage 195 is sized to allow the support shaft of the susceptor assembly 124 to pass through the lower lamp module 104 and to provide a bottom purge.

[0021]

[0026] The susceptor assembly 124 is disposed within the interior space 110 and is configured to support a substrate 150 on a substrate support surface 151. The susceptor assembly 124 is disposed between the upper lamp module 102 and the lower lamp module 104. The lower window 120 is disposed between the susceptor assembly 124 and the lower lamp module 104. The upper window 122 is disposed between the susceptor assembly 124 and the upper lamp module 102. The upper lamp module 102 is disposed above the susceptor assembly 124 and is configured to heat a substrate 150 disposed on the susceptor assembly 124. The upper lamp module 102 includes a plurality of lamp apertures. Each of the plurality of lamp apertures includes a lamp base or socket, and a single lamp 135 is disposed in the lamp base or socket. The orientation of the lamp 135 is generally defined by an imaginary line extending along the filament of the lamp 135 to the tip of the lamp 135. The orientation of the lamps 135 may be parallel or perpendicular to the chamber centerline.

[0022]

[0027] 1B , the EPI processing chamber 100 includes a base plate 114 that includes a substrate transfer passage 116. The substrate transfer passage 116 is disposed through the base plate 114 opposite the cross-gas inlet 196. The substrate transfer passage 116 is formed through the base plate 114. The substrate transfer passage 116 is configured to allow a substrate 150 from a transfer chamber of a cluster tool (not shown) to pass through the substrate transfer passage 116.

[0023]

[0028] A purge gas inlet 192 is located in a susceptor shaft passageway 195 leading to the lower chamber 113 between the susceptor assembly 124 and the surrounding lower lamp module 104 .

[0024]

[0029] Referring again to FIG. 1A, a chamber exhaust passage 152 is disposed through the base plate 114 and is coupled to an exhaust slit assembly (identified by reference numeral 200 in FIGS. 2A-2B). The base plate 114 includes one or more gas injectors 198 disposed therethrough. The gas injectors 198 are configured to supply process gases to the interior space 110. The gas injectors 198 are fluidly connected to one or more process gas sources. The lower chamber exhaust passage 152 is disposed opposite the substrate transfer passage 116 and connects the exhaust slit assembly 200 in the lower chamber to an exhaust pump (not shown). The exhaust pump may also be coupled and in fluid communication with any of the openings of the upper chamber exhaust passage.

[0025]

[0030] 2A is a simplified schematic top view of a portion of a substrate processing system 199, including an EPI processing chamber 100 and an exhaust slit assembly 200. A precursor activation device 180 (see FIG. 1C) is coupled to the EPI processing chamber 100 via a supply line 190. When gases reach a plasma generating region above the substrate 150, they are excited to form a plasma. Downstream of the plasma generating region, gas neutrals, gas ions, and gas radicals flow from the plasma generating region toward the exhaust slit assembly 200.

[0026]

[0031] A flow assembly 125 is disposed inside a chamber inlet 175 that extends through the base plate 114 of the chamber body 108 to flow process gases from the precursor activation device 180 to the processing region 129 of the EPI processing chamber 100. The flow assembly 125 is configured to reduce flow restriction or control the flow distribution of gases flowing into the EPI processing chamber 100.

[0027]

[0032] The EPI processing chamber 100 has a distribution pumping structure 127 for removing process gases from the EPI processing chamber 100. The distribution pumping structure 127 includes an exhaust slit assembly 200. The exhaust slit assembly 200 is disposed adjacent a second surface of the base plate 114 of the chamber body 108. The exhaust slit assembly 200 is configured to control the distribution of gases flowing from the flow assembly 125 across the substrate 150 to the pumping port 128.

[0028]

[0033] 2A-2B are perspective views of an exhaust slit assembly 200. The exhaust slit assembly 200 has a body 201. The body 201 has an exhaust opening 210 (i.e., an exhaust tunnel). The exhaust slit assembly 200 may be fabricated from a material such as quartz or silica to reduce interaction with process gases. In embodiments for use with nitrogen radicals, the exhaust slit assembly 200 may be made from a nitridation-resistant material (such as silicon nitride).

[0029]

[0034] The exhaust slit assembly 200 may optionally include a blocker plate 126. The blocker plate 126 promotes the formation of a layer of uniform thickness on the substrate 150. For example, without the blocker plate 126, the layer at the center of the substrate 150 may be up to significantly thicker than the layer at the edge of the substrate 150. The blocker plate 126 maintains the spread of the gas flow to substantially cover the edge portion of the substrate, thereby improving thickness uniformity.

[0030]

[0035] The exhaust opening 210 may be elongated and may have a shape similar to a dumbbell or dogbone. The shape of the exhaust opening 210 in the exhaust slit assembly 200 varies the conductance from the center to the edge of the opening 210, thereby improving the thickness uniformity of the deposited material layer. In one embodiment, the shape of the exhaust opening 210 can be changed during processing to adjust the conductance profile. In another example, the shape of the exhaust opening 210 is fixed to set the conductance profile of the exhaust slit assembly 200 in the EPI processing chamber 100.

[0031]

[0036] The shape of the opening 210, i.e., the dogbone shape, can lie in a plane parallel to the sidewall 115 of the chamber body 108. For example, the exhaust opening 210 can be a geometrically flat opening 209. Alternatively, the shape of the exhaust slit assembly 200 can extend from the sidewall 115 to the pumping port 128. Optionally, a small plenum 238 can be present around the pumping port 128. The dogbone shape of the exhaust opening 210 can extend a perpendicular line from the sidewall 115 to the pumping port 128, or alternatively, to the plenum 238. In this manner, the shape can be more easily formed in the exhaust slit assembly 200 by machining.

[0032]

[0037] In yet another example, the shape of the opening 210 may lie within the curved plane of the interior space of the chamber body 108 (as shown by the curved opening 208). The shape may be provided by a plate such that a dogbone shape simply follows the opening 210. Alternatively, the shape may extend from the opening to the pumping port 128, or alternatively, to the plenum 238. In this manner, the flow of exhaust through the exhaust slit assembly 200 may be better controlled.

[0033]

[0038] The shape of the opening 210 has been found to directly affect the flow of process gases across the processing region 129 of the EPI processing chamber 100. By configuring the exhaust slit opening 210 to have a dumbbell or dogbone shape, the conductance can be controlled from the center to the edge. The conductance profile of the opening 210 may be static or may vary during processing. The shape of the opening 210 is described below in connection with an elevation view of the opening 210.

[0034]

[0039] FIG. 3 shows two elevation views of the opening of the exhaust slit assembly shown in FIGS. 2A and 2B. The opening 210 has a contour 320. The opening 210 has outer edges 391 and a center 398 defined along a centerline 399 of the opening 210. The outer edges 391 are located on both the left and right sides of the center 398 of the opening 210. That is, there are two outer edges 391. The contour 320 of the opening 210 is narrower at the center 398 than the outer edges 391. The contour 320 may be curved, as shown in the curved opening 208 of FIG. 2A, or flat, as shown in the flat opening 209 of FIG. 2B. The contour 320 may be symmetrical about the centerline 399. For simplicity, the contour 320 may be divided into four areas. The four areas include a left side portion 385, a left center portion 384, a right center portion 383, and a right side portion 382. The left center portion 384 is defined to the left of the center 398 of the opening 210. The right center portion 383 is defined to the right of the center 398 of the opening 210.

[0035]

[0040] The left side 385 and the right side 382 may have rectangular shapes. The left side 385 of the profile 320 may or may not be a mirror image of the right side 382. Thus, the profile 320 may be symmetrical. Alternatively, the profile 320 may be asymmetrical. For example, the left side 385 and the right side 382 of the profile may not be equal in size or shape. The left center portion 384 and the right center portion 383 may have a truncated bell shape, i.e., a trapezoidal shape with an arcuate or concave leg connecting two bases, i.e., a truncated funnel shape. The left center portion 384 of the profile 320 may or may not be a mirror image of the right center portion 383, and the right center portion 383 and the left center portion 384 share a short side along the centerline 399. Overall, the combined shape of left portion 385, left center portion 384, right center portion 383, and right portion 382 forms a dumbbell or dogbone shape.

[0036]

[0041] The left portion 385 can extend between about 25% and about 35% (e.g., about 30%) of the distance from the outer edge 391 to the center 398. Similarly, the right portion 382 can extend between about 25% and about 35% (e.g., about 30%) of the distance from the outer edge 391 to the center 398. The left center portion 384 can extend about 70% of the distance from the center 398 to the outer edge 391 of the opening 210. Similarly, the right center portion 383 can extend about 70% of the distance from the center 398 to the outer edge 391.

[0037]

[0042] A central height 386 of the opening 210 is defined along a vertical centerline 399 at the center 398 of the opening 210. A peripheral height 381 of the opening 210 is defined by outer edges 391 of the opening 210 on either side of the opening. The central height 386 and peripheral height 381 of the opening 210 have lengths defined perpendicular to the chamber body 108, i.e., in the same direction as the centerline 399.

[0038]

[0043] The central height 386 can vary from approximately 0.00 mm, when the central height 386 of the opening 210 is plugged or closed, to approximately 14.00 mm, when the central height 386 is fully open and no longer has a dogbone shape. In one example, the central height 386 of the opening 210 can be between approximately 3.00 mm and approximately 9.00 mm. In another example, the central height 386 of the opening 210 can be between approximately 3.9 mm and approximately 8.4 mm. The outer edge height 381 of the opening 210 can be between approximately 10.00 mm and approximately 14.00 mm. However, it has been found that a larger size for the outer edge height 381 of the opening 210 compared to the size of the central height 386 of the opening 210 provides the most desirable processing results on the substrate.

[0039]

[0044] Simulations and tests were conducted in which a portion of the opening 210 of the exhaust slit assembly 200 was blocked at the center 398 of the opening 210. Blocking an area of ​​the exhaust slit tunnel with the blocker plate 126 provided a wider, rectangular deposition profile compared to the plume-shaped deposition thickness profile observed under the same conditions when the blocker plate 126 was not used. The blocker plate 126 created a recirculation zone above the substrate, particularly near the blocked area. Similarly, simulation tests were conducted with various opening ratios between the center height 386 and the outer edge height 381. In these tests, the exhaust velocity from the center 398 to the outer edge 391 of the exhaust opening 210 was measured, and the opening profile was found to affect the flow. The opening ratio was varied from 0%, when the center of the blocker plate 126 was completely blocked, to 100%, when the center height 386 was equal to the outer edge height 381. For example, ratios of 65% opening at center height 386, 60% opening at center height 386, 50% opening at center height 386, and up to 30% opening at center height 386 were all measured and compared to a conventional opening of 100% opening at center height 386. The results are summarized in Table 1 below. TIFF2025533601000002.tif83170Table 1

[0040]

[0045] Table 1 shows that a central opening between about 25% and about 40% provides a flat flow profile, while a central opening between about 50% and about 70% produces a dome-shaped flow profile with reduced center-to-edge variation. The outer edge height 381 is equal to or greater than the central height 386. The ratio of the central height 386 to the outer edge height 381 (central height 386 / outer edge height 381) can be between about 30% and about 40%. In another example, the ratio of the central height 386 to the outer edge height 381 is between about 50% and about 70%. In yet another example, the ratio of the central height 386 to the outer edge height 381 is between about 50% and about 80%.

[0041]

[0046] While the foregoing description is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope of the disclosure, the scope of which is determined by the claims that follow. As is apparent from the foregoing summary and specific embodiments, while forms of the present disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, no limitations on the present disclosure are intended. Similarly, the word "comprising" is considered synonymous with the word "including."

[0042]

[0047] Certain embodiments and features are described using a set of upper numerical limits and a set of lower numerical limits. It should be recognized that ranges including any two value combinations (e.g., any lower value with any upper value, any two lower values, and / or any two upper values) are contemplated unless otherwise indicated. Specific lower limits, upper limits, and ranges are set forth in one or more of the claims below.

Claims

1. 1. A processing chamber comprising: a chamber body, the chamber body comprising: A first surface; a second surface opposite the first surface; and A window assembly; a base, wherein the first surface, the second surface, the window assembly, and the base define and enclose a thermal treatment region, and the processing chamber further comprises: a flow assembly disposed adjacent the first surface, the flow assembly configured to introduce a process gas into the thermal treatment region; and an exhaust slit assembly disposed adjacent the second surface; The exhaust slit assembly comprises: an opening communicating with the heat treatment area, the opening having a center and outer edges, the center and the edges of the opening being defined vertically between the window assembly and the base, and an outer height at the edges of the opening being at least 30% greater vertically than a central height at the center of the opening; Processing chamber.

2. The opening is The processing chamber of claim 1 , further comprising a blocker plate disposed at the center of the opening.

3. 10. The processing chamber of claim 1, wherein a ratio of the central height of the opening to the outer height of the opening is between about 30% and about 80%.

4. 10. The processing chamber of claim 1, wherein a ratio of the central height of the opening to the outer height of the opening is between about 30% and about 40%.

5. 10. The processing chamber of claim 1, wherein a ratio of the central height to the outer height of the opening is between about 50% and about 70%.

6. The opening further comprises: The left side and The left center and Right center and 10. The processing chamber of claim 1, further comprising: a right side portion, wherein the left side and the right side have a rectangular shape, and the left center portion and the right center portion have a trapezoidal shape with curved legs between two bases.

7. 7. The processing chamber of claim 6, wherein the left side and the right side each extend between about 25% and about 35% of the distance from the outer edge to the center, and the left center and the right center each extend between about 75% and about 65% of the distance from the center to the outer edge.

8. The processing chamber of claim 6 , wherein the left side, the left center side, the right center side, and the right side form a dogbone shape.

9. 1. An exhaust slit assembly comprising: a body having an elongated opening configured to receive a gas, the elongated opening having a dog-bone shape and having a central opening height located at a center of the elongated opening and an outer opening height located along an outer edge of the elongated opening, the outer opening height exceeding the central opening height by at least 30% in a vertical direction; Exhaust slit assembly.

10. 10. The exhaust slit assembly of claim 9, wherein the dogbone shape of the elongated opening is asymmetrical such that a left edge of the opening and a right edge of the opening are not equal.

11. 10. The exhaust slit assembly of claim 9, wherein a ratio of the central height of the opening to the outer height of the opening is between about 30% and about 80%.

12. 10. The exhaust slit assembly of claim 9, wherein the ratio of the central height to the outer height of the opening is between about 30% and about 40%.

13. 10. The exhaust slit assembly of claim 9, wherein the ratio of the central height to the outer height of the opening is between about 50% and about 70%.

14. 10. The exhaust slit assembly of claim 9, wherein the ratio of the central height to the outer height of the opening is about 0%.

15. The elongated opening further comprises: The left side and The left center and Right center and and a right side portion, wherein the left side and the right side have a rectangular shape and the left central portion and the right central portion have a trapezoidal shape with curved legs between two bases.

16. 16. The exhaust slit assembly of claim 15, wherein the left side and the right side each extend approximately 30% of the distance from the outer edge to the center, and the left center and right center each extend approximately 70% of the distance from the center to the outer edge.

17. 1. A method for thermally processing a substrate, comprising: flowing a process gas into the processing chamber through the first opening and into a processing region containing the substrate; flowing the process gas laterally across the substrate from the first opening to a second opening of the processing chamber, the second opening having a higher conductance at an outer edge of the second opening than at a center of the second opening; heating the substrate in the presence of the process gas; depositing a layer of material on the heated substrate in the presence of the process gas; A method comprising:

18. 20. The method of claim 17, further comprising flowing the process gas over a blocker plate centrally located in the second opening.

19. 18. The method of claim 17, wherein the second opening has an outer height and a central height, and the ratio of the central height to the outer height is between about 30% and about 80%.

20. 18. The method of claim 17, further comprising: varying the conductance of the second opening by varying a center height of the second opening.

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