Gas flow improvements for process chambers

Abstract

A process chamber comprising: a chamber body enclosing an interior space; a substrate support disposed in the interior space, the interior space including a lower interior space below the substrate support and an upper interior space above the substrate support; a first purge gas line configured to provide a first flow of purge gas to the lower interior space; and a gas flow ring disposed around an outer edge of the substrate support, the gas flow ring including a ring-shaped body, a top surface, a bottom surface, a first overlapping portion extending from a first interior sidewall of the ring-shaped body, and a second overlapping portion extending from a second sidewall of the ring-shaped body, the first overlapping portion and the second overlapping portion overlapping and spaced apart from each other to form a gas flow channel extending from the bottom surface to the top surface of the gas flow ring.

Description

[Technical Field]

[0001]

[0001] Embodiments of the present disclosure generally relate to equipment (e.g., gas flow rings) that provide improvements regarding purge gas flow within a process chamber. Such improvements can reduce the flow rate of purge gas and reduce deposition on the backside of a substrate support. [Background technology]

[0002]

[0002] Purge gas is often provided below a substrate support in a process chamber to prevent process gas from entering the space below the substrate support within the process chamber. If process gas enters the space below the substrate support, problems such as unintended deposition on surfaces below the substrate support, such as deposition on the backside of the substrate support, can occur. Such unintended deposition increases the frequency with which chamber cleaning is required. Furthermore, unintended deposition on the backside of the substrate support can reduce the uniformity of processes performed on substrates positioned on the substrate support. For example, deposition on the backside of the substrate support can reduce the uniformity (e.g., thickness uniformity) of depositions performed on substrates positioned on that substrate support.

[0003]

[0003] Increasing the flow rate of purge gas typically reduces problems associated with process gases entering the space below the substrate support, such as deposition on the backside of the substrate support. However, increasing the flow rate of purge gas increases costs and downtime for chamber cleaning, as discussed above.

[0004] Therefore, there is a need for an improved process chamber outfitting that can reduce the requirements for purge gas flow rate without increasing the need for process chamber cleaning. Summary of the Invention

[0005]

[0005] In one embodiment, a process chamber is provided, comprising: a chamber body enclosing an internal space; a substrate support disposed in the internal space, the internal space including a lower internal space below the substrate support and an upper internal space above the substrate support; a first purge gas line configured to provide a first flow of purge gas to the lower internal space; and a gas flow ring disposed around the outer edge of the substrate support, the gas flow ring including a ring-shaped body, a top surface, a bottom surface, a first overlapping portion extending from a first internal side wall of the ring-shaped body, and a second overlapping portion extending from a second internal side wall of the ring-shaped body, the first overlapping portion and the second overlapping portion overlapping and spaced apart from each other to form a gas flow channel extending from the bottom surface to the top surface of the gas flow ring.

[0006]

[0006] In another embodiment, a process chamber is provided that includes a chamber body enclosing an internal space, a substrate support disposed in the internal space, the internal space including a lower internal space below the substrate support and an upper internal space above the substrate support, a first purge gas line configured to provide a first flow of purge gas to the lower internal space, and a gas flow ring disposed around the outer edge of the substrate support, the gas flow ring including a ring-shaped body, a top surface, a bottom surface, and gas flow channels extending from the bottom surface to the top surface of the gas flow ring, with no line of sight extending through the channels.

[0007]

[0007] In another embodiment, a process kit for processing a substrate is provided, comprising one or more liners forming a substantially annular structure, and a gas flow ring positioned on an upper surface of the one or more liners, the gas flow ring including a ring-shaped body, a top surface, a bottom surface, a first overlapping portion extending from a first inner side wall of the ring-shaped body, and a second overlapping portion extending from a second inner side wall of the ring-shaped body, the first overlapping portion and the second overlapping portion being spaced apart from each other to form a gas flow channel extending from the bottom surface to the top surface of the gas flow ring. [Brief explanation of the drawings]

[0008]

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

[0009] [Figure 1]

[0009] FIG. 1 is a schematic cross-sectional side view of an exemplary process chamber that may be used to perform various embodiments of the deposition processes described in this disclosure. [Figure 2A]

[0010] 2 is a top view of the gas flow ring of FIG. 1 positioned around the outer edge of the substrate support 115 of FIG. 1 according to one embodiment. [Figure 2B]

[0011] 2B is a partial cross-sectional side view of a portion of the gas flow ring of FIG. 2A taken through section line 2B of FIG. 2A, according to one embodiment. [Figure 2C]

[0012] 2 is a top view of an alternative gas flow ring positioned around the outer edge of the substrate support of FIG. 1 according to one embodiment. [Figure 2D]

[0013] 2 is a top view of an alternative gas flow ring positioned over a portion of the substrate support of FIG. 1 according to one embodiment. [Figure 2E]

[0014] FIG. 10 is a partial cross-sectional side view of an alternative gas flow ring including alternative gas flow channels according to one embodiment. [Figure 2F]

[0015] FIG. 10 is a partial cross-sectional side view of an alternative gas flow ring including alternative gas flow channels according to one embodiment.

[0010]

[0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0017] Embodiments of the present disclosure generally relate to an apparatus for improving purge gas flow within a process chamber. A gas flow ring (also called a preheat ring) can be positioned around a substrate support within the process chamber. The gas flow ring can be spaced from the substrate support so that purge gas provided below the substrate support can flow around the outer edge of the substrate support. A portion of the purge gas can flow between the substrate support and the ring, and another portion can flow through channels in the ring. For example, the gas flow ring can include gas flow channels configured to allow purge gas to flow from a position below the gas flow ring to a position above the gas flow ring. The gas flow channels can be formed by opposing overlapping portions of the ring. The upper overlapping portion can directly overlap the lower overlapping portion. Such an overlapping configuration can prevent at least a portion of the gas from following a single straight line through the channels. A gas flow ring with overlapping portions has been shown to improve the balance of purge gas flow around a substrate positioned on the substrate support, which can help improve the uniformity of a process (e.g., deposition) performed on the substrate. Additionally, the gas flow ring can reduce the amount of other gases (e.g., precursor gases) that diffuse into the region below the substrate support, which helps reduce unintentional deposition, such as deposition on the backside of the substrate support. Such reduction in unintentional deposition can help reduce the amount of downtime used to clean components such as the process chamber and the substrate support.

[0012]

[0018] 1 is a schematic cross-sectional side view of an exemplary process chamber 100 that may be used to carry out various embodiments of the deposition processes described in this disclosure. The process chamber 100 may be used to perform chemical vapor deposition, such as epitaxial deposition and etching processes, as well as other processes.

[0013]

[0019] The chamber 100 includes a housing structure 102 formed from a process-resistant material, such as aluminum or stainless steel. The housing structure 102 encloses an inner chamber 104. In some embodiments, the inner chamber 104 can be formed from quartz. The inner chamber 104 can include an upper chamber 106 and a lower chamber 107.

[0014]

[0020] The process chamber 100 further includes a substrate support assembly 112. The substrate support assembly 112 can include a substrate support 115 and a shaft 119 coupled to the substrate support 115. In some embodiments, the substrate support 115 can be a susceptor. In some embodiments, the shaft 119 is coupled to an actuator (not shown) that can be used to rotate the shaft 119. Rotation of the shaft 119 rotates the substrate support 115, allowing a substrate 114 positioned on the substrate support 115 to rotate during processing, which can increase process uniformity. The substrate 114 can include a processing surface 116 on which a process (e.g., deposition) is performed. The substrate support 115 can be fabricated from a ceramic material or a graphite material coated with a silicon material, such as silicon carbide.

[0015]

[0021] The upper chamber 106 includes a processing volume 110. The lower chamber 107 includes an inner volume 108. The processing volume 110 and the inner volume 108 are collectively referred to as the interior space. The interior space includes the space enclosed by the inner chamber 104 (also referred to as the chamber body). The processing volume 110 is also referred to as the upper interior space, which is located above the substrate support 115. Similarly, the inner volume 108 is also referred to as the lower interior space, which is located below the substrate support 115.

[0016]

[0022] The process chamber 100 may further include heating equipment, such as an upper lamp module 118A and a lower lamp module 118B. In one embodiment, the upper lamp module 118A and the lower lamp module 118B are infrared lamps. Radiation from the lamp modules 118A and 118B passes through an upper window 120 of the upper chamber 106 and through a lower window 122 of the lower chamber 107. In some embodiments, the windows 120, 122 may be formed of quartz. In some embodiments, a cooling gas for the upper chamber 106 may enter through an inlet 124 and exit through an outlet 126; a similar configuration (not shown) for the cooling gas may be used for the lower chamber 107.

[0017]

[0023] The process chamber 100 may further include a gas distribution assembly 128. The gas distribution assembly 128 may provide precursor gases to the processing volume 110 of the inner chamber 104. Processing by-products may be removed from the processing volume 110 by an exhaust assembly 130, which is typically in communication with a vacuum source (not shown). Precursor reactant gases and etching gases, as well as carrier and vent gases for the chamber 100, may enter through the gas distribution assembly 128 and exit through the exhaust assembly 130.

[0018]

[0024] The process chamber 100 may further include a first purge gas line 180 and a second purge gas line 190 to provide one or more purge gases to the inner volume 108 of the lower chamber 107. The first purge gas line 180 may be connected to a first purge gas source 181. The second purge gas line 190 may be connected to a second purge gas source 191. The first purge gas line 180 may enter the inner volume 108 (lower interior space) at a location outside the lower chamber 107 through a side of the inner chamber 104. Such an outside location may be closer to the outer edge 117 ( FIG. 2A ) of the substrate support 115 than to the center of the substrate support 115. The second purge gas line 190 may enter a central location of the inner volume 108 below a central portion of the substrate support 115, for example, near the shaft 119 of the substrate support assembly 112. The flow of purge gas through the first purge gas line 180 and / or the second purge gas line 190 can be adjusted to balance the purge gas to different parts of the inner volume 108 (e.g., different areas around the edge of the substrate support 115) so that the purge gas can prevent precursor gas from entering the processing volume 110 of the upper chamber 106 into the inner volume 108 of the lower chamber 107.

[0019]

[0025] The chamber 100 may also include multiple liners 132A-132G that protect the processing volume 110 from a metal wall 134 that surrounds the processing volume 110. In one embodiment, the liners 132A-132G comprise a process kit that covers all metal components that may communicate with or otherwise be exposed to the processing volume 110.

[0020]

[0026] One or more gases may be provided to the processing volume 110 from the first gas source 135A and the second gas source 135B, through the baffle liner 132G, the inject insert liner assembly 132F, and through one or more openings 136A and 136B formed in the injector liner 132E. The one or more openings 136A and 136B formed in the injector liner 132E are connected to outlets configured for the laminar flow path 133A or the jet flow path 133B. In some embodiments, the gases from the first gas source 135A and the second gas source 135B may be premixed before entering the chamber and then supplied to the processing volume 110 through the same gas supply line. The openings 136A and 136B may be configured to provide individual or multiple gas streams with various parameters, such as viscosity, density, or composition. In one embodiment, the openings 136A and 136B may be distributed around the gas distribution assembly 128.

[0021]

[0027] Each of the flow paths 133A, 133B can be configured to flow along an axis A′ toward the exhaust liner 132D. The axis A′ is substantially perpendicular to the longitudinal axis A″ of the chamber 100. The flow of the flow paths 133A, 133B can be directed toward an exhaust flow path 133C that is directed toward an exhaust port 138 of an exhaust plenum 137 formed in the exhaust liner 132C. The plenum 137 is connected to an exhaust or vacuum pump (not shown). The inject insert liner assembly 132F can be disposed through and partially supported by the inkjet cap 129. Additionally, although only two gas sources 135A, 135B are shown in FIG. 1 , the process chamber 100 can be adapted to include more than two gas sources.

[0022]

[0028] The process chamber 100 further includes a gas flow ring 200 (also referred to as a preheat ring) disposed around the substrate support 115. In some embodiments, the bottom surface of the gas flow ring 200 can be positioned on one or more liners (e.g., liner 132B). The gas flow ring 200 can be spaced from the outer edge 117 of the substrate support 115 (see FIG. 2A) by a gap G. The gas flow ring 200 can be used to control the flow of purge gas within the process chamber 100. Purge gas provided from purge gas lines 180, 190 flows into the inner volume 108 of the lower chamber 107, through the gap G into the processing volume 110 of the upper chamber 106, and then exits the processing volume 110 through the exhaust assembly 130. The gas flow ring 200 further includes gas flow channels 220 (see FIGS. 2A and 2B) that also allow purge gas to flow along a similar path.

[0023]

[0029] 1 (also referred to as a radial direction from the center of the substrate support 115), the gap G can have a width of about 0.25 mm to about 12 mm, for example, about 0.5 mm to about 6.5 mm. In some embodiments, the gap G can extend around the outer edge 117 (see FIG. 2A) of the substrate support 115 with a substantially constant size (i.e., within 2.5% of the average size around the entire circumference of the substrate support 115). In other embodiments (see FIG. 2C), the size of the gap varies significantly around the substrate support 115.

[0024]

[0030] Figure 2A is a top view of a gas flow ring 200 positioned around the outer edge 117 of the substrate support 115 of Figure 1, according to one embodiment. Figure 2B is a partial side cross-sectional view of a portion of the gas flow ring 200 of Figure 2A through section line 2B of Figure 2A, according to one embodiment.

[0025]

[0031] The gas flow ring 200 includes a ring-shaped body 230. The ring-shaped body 230 may form a majority of the gas flow ring 200. For example, in some embodiments, the ring-shaped body 230 may form more than 90% of the total circumference of the gas flow ring 200. The gas flow ring 200 further includes an inner edge 201 and an outer edge 202. The inner edge 201 of the gas flow ring 200 is spaced from the outer edge 117 of the substrate support 115 by the gap G described above. The gas flow ring 200 further includes gas flow channels 220 that may allow purge gas to flow from below the substrate support 115 to above the substrate support 115.

[0026]

[0032] 2B , the gas flow ring 200 includes a top surface 205 and a bottom surface 206. The ring-shaped body 230 may further include a first interior sidewall 231 and a second interior sidewall 232. The first interior sidewall 231 may be opposite the second interior sidewall 232. The gas flow ring 200 further includes a first overlapping portion 211 and a second overlapping portion 212. The first overlapping portion 211 may extend from the first interior sidewall 231 to a leading edge 215 of the first overlapping portion 211. The second overlapping portion 212 may extend from the second interior sidewall 232 to a leading edge 216 of the second overlapping portion 212. The first overlapping portion 211 may overlap (i.e., be separated only vertically) from the second overlapping portion 212. The space between first overlapping portion 211 and second overlapping portion 212 can form a portion of gas flow channel 220. Overall, gas flow channel 220 is defined by the space created by the distance of (1) first interior sidewall 231 and first overlapping portion 211 from (2) second interior sidewall 232 and second overlapping portion 212.

[0027]

[0033] The leading edge 215 of the first overlapping portion 211 can be horizontally spaced apart from the second interior sidewall 232 by a distance of about 0.25 mm to about 20 mm, e.g., about 0.5 mm to about 10 mm. Similarly, the leading edge 216 of the second overlapping portion 212 can be horizontally spaced apart from the first interior sidewall 231 by a distance of about 0.25 mm to about 20 mm, e.g., about 0.5 mm to about 10 mm. The first overlapping portion 211 can be vertically spaced apart from the second overlapping portion 212 by a distance of about 0.25 mm to about 8 mm, e.g., about 0.5 mm to about 4 mm. In some embodiments, the first interior sidewall 231 can be horizontally spaced apart from the second interior sidewall 232 by a distance of about 4.5 mm to about 30 mm.

[0028]

[0034] 1 and 2B , depending on the design of the gas flow channels 220, the gas flow ring 200 can completely prevent gas from flowing in a straight path from the inner volume 108 of the lower chamber 107 to the processing volume 110 of the upper chamber 106, or can substantially reduce the amount of such gas. In some embodiments of the gas flow ring 200, there is no straight path (i.e., no line of sight) from the inner volume 108 of the lower chamber 107 to the processing volume 110 of the upper chamber 106. In some other embodiments, there is no line of sight path through the channels 220 at at least some radial positions of the channels 220, and the center of the gas flow ring 200 is used to determine the radial distance. In some embodiments, there is no line of sight path through the channels 220 at at least some positions along the inner edge 201 of the gas flow ring 200.

[0029]

[0035] 2C is a top view of an alternative gas flow ring 200C positioned around the outer edge 117 of the substrate support 115 of FIG. 1 , according to one embodiment. The arrangement of this alternative gas flow ring 200C and substrate support 115 is the same as that described above for FIG. 2A , except that the size of the gap G between the gas flow ring 200C and the outer edge 117 of the substrate support 115 varies significantly around the outer edge 117 of the substrate support 115. This variation in the size of the gap G allows for better control of the flow of purge gas around the outer edge 117 of the substrate support 115. For example, using a smaller gap near the gas inlet openings 136A, 136B (see FIG. 1 ), far from the exhaust port 138, can prevent dispersion of the gas flow passing over the wafer and reduce dilution of the precursor gas. Reduced dilution of the precursor gas can increase the growth rate of the deposition and improve throughput. In some of these embodiments, the gap G at a first position around the substrate support 115 can be about 10% to about 80%, such as about 20% to about 50%, of the size of the gap G at a second position around the substrate support 115. For example, as shown in FIG. 2C , the size of the gap G at the first position G1 is substantially smaller (e.g., less than 50%) than the size of the gap G at the second position G2. In some embodiments, the gas flow ring 200C can be positioned around the substrate support 115 such that the gap G has a larger size at a position closer to the exhaust port 138 (e.g., position G2) relative to a position farther from the exhaust port 138 (e.g., position G1), e.g., near the gas inlet side.

[0030]

[0036] In some embodiments, gas flow ring 200C is the same as gas flow ring 200A, and gas flow ring 200C is positioned such that the center of gas flow ring 200C is aligned with the center of substrate support 115. In other embodiments, gas flow ring 200C is physically different from gas flow ring 200 described above. For example, in one embodiment, inner edge 201C of gas flow ring 200 can have a non-circular shape to control the size of the gap around outer edge 117 of substrate support 115.

[0031]

[0037] 2D is a top view of another gas flow ring 200D positioned over a portion of the substrate support 115 of FIG. 1 , according to one embodiment. As shown, a portion of the gas flow ring 200D overlaps a portion of the top surface of the substrate support 115. In the figure, the outer edge 117 of the substrate support 115 is not visible in the configuration shown in FIG. 2D , but is shown as a dashed line indicating the portion of the outer edge 117 of the substrate support 115 that is hidden in the top view of FIG. 2D . The gas flow ring 200D is positioned at a different vertical position than the substrate support 115. In some embodiments, the amount of overhang of the gas flow ring 200D over the substrate support 115 can vary around the outer edge 117 of the substrate support 115. Although the vertical gap between the gas flow ring 200D and the substrate support 115 is not shown, this gap can have a vertical dimension similar to the horizontal dimension of the gap G described above with reference to FIGS. 1 and 2A .

[0032]

[0038] The addition of gas flow channels 220 to the above-described gas flow ring provides better control of purge gas within the process chamber compared to previous gas flow rings configured with a linear path (e.g., a straight, vertical path) that opens completely from below the gas flow ring to above the gas flow ring. The improved control of purge gas within the process chamber provided by such a gas flow ring reduces the precursor gas that can enter the lower interior space of the process chamber (i.e., below the substrate support) for a given purge gas flow rate, which can prevent unintended deposition on components within the lower chamber, such as the backside of the substrate support 115. The above-described purge gas ring also improves the uniformity of the purge gas flow around the gas flow ring and around the substrate being processed. Furthermore, this improved uniformity can be achieved with a lower purge gas flow rate compared to when conventional purge gas rings are used. In one example, a gas flow ring employing gas flow channels (e.g., gas flow channel 220) with the above-described characteristics reduced purge gas usage by 50%.

[0033]

[0039] Improving the uniformity of the purge gas around the substrate can also improve the uniformity of the process (e.g., deposition) performed on the substrate. Additionally, because the gas flow ring improves uniformity at a lower purge gas flow rate compared to conventional gas flow rings, the above-described purge gas ring can also achieve cost savings through reduced purge gas usage. Furthermore, because precursor diffusion into the region within the lower interior space (e.g., below the substrate support) is reduced, a higher concentration of precursor gas above the substrate support is maintained, which can allow the process (e.g., deposition) to be completed more quickly and less precursor gas is wasted.

[0034]

[0040] 2E is a partial cross-sectional side view of another gas flow ring 200E including gas flow channels 220E, according to one embodiment. The gas flow ring 200E may be the same as the gas flow ring 200 described above, except that the gas flow ring 200E includes gas flow channels 220E, which are in contrast to the gas flow channels 220 described above with reference to FIGS. 2A and 2B. The gas flow channels 220E differ from the gas flow channels 220 in that a protrusion 219 extends into the channels 220E from the second overlapping portion 212 toward the first overlapping portion 211. The protrusion 219 in the illustration is at the leading edge 216 of the second overlapping portion 212, but may be located at a different position on the second overlapping portion 212. Alternatively, the protrusion 219 may be located on the first overlapping portion 211. The protrusion 219 can further restrict the flow of gas through the channel 220E compared to the flow of gas through the channel 220 shown in FIG. 2B, thereby further controlling the flow of purge gas around the substrate support 115.

[0035]

[0041] 2F is a partial cross-sectional side view of an alternative gas flow ring 200F including gas flow channels 220F, according to one embodiment. Gas flow ring 200F may be the same as gas flow ring 200 described above, except that gas flow ring 200F includes gas flow channels 220F, as opposed to gas flow channels 220 described above with reference to FIGS. 2A and 2B. Gas flow channels 220F differ from gas flow channels 220 in that multiple protrusions extend into channels 220F from overlapping portions 211, 212. First overlapping portion 211 includes first and second protrusions 241, 242 that extend downward in the Z direction toward second overlapping portion 212. Second overlapping portion 212 includes first and second protrusions 251, 252 that extend upward in the Z direction toward first overlapping portion 211. The size of the protrusions may be increased to further restrict the flow of gas through gas flow channel 220F. Protrusions 241, 242, 251, 252 can further restrict the flow of gas through channel 220F compared to the flow of gas through channel 220 shown in FIG. 2B , thereby further controlling the flow of purge gas around substrate support 115. In some embodiments, more (e.g., 6 or 10 protrusions) or fewer (e.g., 2 or 3 protrusions) can be used. In one embodiment including two protrusions, each overlapping portion 211, 212 includes a protrusion at a corresponding leading edge 215, 216 that extends into the gas flow channel.

[0036]

[0042] Each protrusion in the gas flow channel of Figures 2E and 2F can increase the tortuosity of the gas flow path, which can further prevent diffusion of precursor gas from above the substrate support 115 (see Figure 1) to the region below the substrate support 115. Such diffusion of precursor gas is reduced by the protrusions, allowing less purge gas to be used to achieve the same result, which provides cost benefits to production. Reducing precursor gas diffusion also reduces the amount of downtime used to clean the chamber and also increases the concentration of purge gas above the substrate, which increases the efficiency of the process as discussed above.

[0037]

[0043] While the foregoing description is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A process chamber comprising: a chamber body enclosing an interior space; a substrate support disposed in the interior space, the interior space including a lower interior space below the substrate support and an upper interior space above the substrate support; a first purge gas line configured to provide a first flow of purge gas to the lower interior space; and a gas flow ring disposed around an outer edge of the substrate support, a ring-shaped body, a top surface, a bottom surface, a first overlapping portion extending from a first inner sidewall of the ring-shaped body, and a second overlapping portion extending from a second inner sidewall of the ring-shaped body; the first overlapping portion and the second overlapping portion overlap with a space therebetween to form a gas flow channel extending from the bottom surface to the top surface of the gas flow ring. Gas Flow Ring A process chamber comprising:

2. 10. The process chamber of claim 1, wherein a leading edge of the first overlapping portion is horizontally spaced from the second interior sidewall by a distance of about 0.5 mm to about 10 mm.

3. 10. The process chamber of claim 1, wherein the first overlapping portion is vertically spaced from the second overlapping portion by a distance of about 0.5 mm to about 4 mm.

4. 10. The process chamber of claim 1, wherein the gas flow ring is spaced from an outer edge of the substrate support by a gap.

5. 5. The process chamber of claim 4, wherein the gap size at a first location around the outer edge of the substrate support is about 10% to about 50% of the gap size at a second location around the outer edge of the substrate support.

6. 10. The process chamber of claim 1, wherein the first overlapping portion or the second overlapping portion includes a first protrusion extending into the gas flow channel toward the other overlapping portion.

7. the first overlapping portion includes a first protrusion extending into the gas flow channel toward the second overlapping portion; the second overlapping portion includes a second protrusion extending into the gas flow channel toward the first overlapping portion. The process chamber of claim 1 .

8. 10. The process chamber of claim 1, wherein at least a portion of the gas flow ring overlaps a portion of a top surface of the substrate support.

9. a second purge gas line configured to provide a second flow of purge gas to the lower interior volume; the first purge gas line is configured to provide a first flow of the purge gas to a location outside the lower interior space; the second purge gas line is configured to provide a second flow of the purge gas to a central location of the lower interior space that is located below a central portion of the substrate support, and the outer location is closer to an outer edge of the substrate support than to a center of the substrate support. The process chamber of claim 1 .

10. 1. A process chamber comprising: a chamber body enclosing an interior space; a substrate support disposed in the interior space, the interior space including a lower interior space below the substrate support and an upper interior space above the substrate support; a first purge gas line configured to provide a first flow of purge gas to the lower interior space; and a gas flow ring disposed around an outer edge of the substrate support, 1. A gas flow ring comprising: a ring-shaped body, a top surface, a bottom surface, and gas flow channels extending from the bottom surface to the top surface of the gas flow ring, wherein there are no lines of sight extending through the gas flow channels. A process chamber comprising:

11. 11. The process chamber of claim 10, wherein the width of the gas flow channels at the top surface of the gas flow ring is from about 0.5 mm to about 10 mm.

12. 11. The process chamber of claim 10, wherein the gas flow ring includes a first overlapping portion and a second overlapping portion, the first overlapping portion and the second overlapping portion being spaced apart from one another to form the gas flow channel, and the first overlapping portion being vertically spaced apart from the second overlapping portion by a distance of about 0.5 mm to about 4 mm.

13. The process chamber of claim 10 , wherein the gas flow ring is spaced from an outer edge of the substrate support by a gap.

14. 14. The process chamber of claim 13, wherein the gap size is substantially constant around the outer edge of the substrate support.

15. 14. The process chamber of claim 13, wherein a size of the gap at a first location around the outer edge of the substrate support is about 10% to about 50% of a size of the gap at a second location around the outer edge of the substrate support.

16. 16. The process chamber of claim 15, further comprising an exhaust port, wherein the second location is closer to the exhaust port than the first location is relative to the exhaust port.

17. 11. The process chamber of claim 10, wherein at least a portion of the gas flow ring overlaps a portion of a top surface of the substrate support.

18. a second purge gas line configured to provide a second flow of purge gas to the lower interior volume; the first purge gas line is configured to provide a first flow of the purge gas to a location outside the lower interior space; the second purge gas line is configured to provide a second flow of the purge gas to a central location of the lower interior space that is located below a central portion of the substrate support, and the outer location is closer to an outer edge of the substrate support than to a center of the substrate support. The process chamber of claim 10.

19. 1. A process kit for processing a substrate, comprising: one or more liners forming a substantially annular structure; and a gas flow ring positioned on an upper surface of the one or more liners, a ring-shaped body, a top surface, a bottom surface, a first overlapping portion extending from a first inner sidewall of the ring-shaped body, and a second overlapping portion extending from a second inner sidewall of the ring-shaped body; the first overlapping portion and the second overlapping portion overlap with a space therebetween to form a gas flow channel extending from the bottom surface to the top surface of the gas flow ring. Gas Flow Ring A process chamber comprising:

20. 20. The process kit of claim 19, wherein there are no lines of sight extending through the gas flow channels.

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