Gas diffuser with diffuser gas hole plug for substrate processing

Abstract

Embodiments herein are generally directed to semiconductor manufacturing, and more particularly, gas diffusers for substrate processing chambers. In an embodiment, a gas diffuser includes at least one gas diffuser unit including a fastening aperture through a top surface of the diffusion plate body, a first gas inlet disposed an inlet distance from the fastening aperture, a second gas inlet disposed the inlet distance from the fastening aperture, an aperture plug at a distal end of the fastening aperture, and a gas outlet fluidly coupled to the channel and extending through a bottom surface of the diffusion plate body. In another embodiment, the gas diffuser a plug portion at a distal end of the fastening aperture. In yet another embodiment, a processing chamber includes a gas diffuser coupled to the lid structure including a plug portion disposed in fastening aperture of at least one gas diffuser unit.

Description

GAS DIFFUSER WITH DIFFUSER GAS HOLE PLUG FOR SUBSTRATE PROCESSINGBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to semiconductor manufacturing, and more particularly, gas diffusers for substrate processing chambers.Description of the Related Art

[0002] Center-supported gas diffusers constitute a variant of gas diffusers upheld one or more central rods. This classification of diffuser finds typical application in scenarios necessitating even gas dispersion across a considerable expanse.

[0003] Operational functionality is achieved by center-supported gas diffusers through the extraction of gas from a central supply line, followed by its release via a sequence of nozzles. These nozzles are symmetrically arrayed in a configuration encompassing the central rod(s), formulated to uniformly disperse the gas across the designated region.

[0004] In the context of substrate processing chambers, center-supported gas diffusers are often situated within the chamber ceiling. Integration with a central gas supply line ensures an unceasing gas source. Construction from stainless steel or analogous corrosion-resistant materials is commonplace. Routine inspection and maintenance are standard for ensuring consistent functionality.

[0005] Detrimental implications of particulates or debris on substrate processing encompass contamination, physical damage, process interference, and safety risks, particularly in high-temperature or vacuum settings. Countermeasures are requisite to uphold a debris-free and clean substrate vicinity.

[0006] While center-supported gas diffusers are commonly fashioned from durable materials resistant to wear and corrosion, occasional wear and tear or particle clogging might transpire over time. These scenarios could induce particle or debrisshedding from the diffusers or the central rods, possibly resulting in contamination of the chamber and substrates being processed.

[0007] Accordingly, there is a need for an improved center-supported gas diffuser to reduce particle contamination on the substrate being processed.SUMMARY

[0008] Embodiments herein are generally directed to semiconductor manufacturing, and more particularly, gas diffusers for substrate processing chambers.

[0009] In an embodiment, a gas diffuser is provided. The gas diffuser includes a diffusion plate body, and a diffuser array in the diffusion plate body and including at least one gas diffuser unit, the gas diffuser unit including a fastening aperture through a top surface of the diffusion plate body, a first gas inlet disposed an inlet distance from the fastening aperture, a second gas inlet disposed the inlet distance from the fastening aperture and opposite the first gas inlet, an aperture plug at a distal end of the fastening aperture, a channel fluidly coupled to the first gas inlet and the second gas inlet, and a gas outlet fluidly coupled to the channel and extending through a bottom surface of the diffusion plate body.

[0010] In another embodiment, a gas diffuser is provided. The gas diffuser includes a diffusion plate body, and a diffuser array in the diffusion plate body and including at least one gas diffuser unit, the gas diffuser unit including a fastening aperture through a top surface of the diffusion plate body, a first gas inlet disposed an inlet distance from the fastening aperture, a second gas inlet disposed the inlet distance from the fastening aperture and opposite the first gas inlet, a plug portion at a distal end of the fastening aperture, a channel fluidly coupled to the first gas inlet and the second gas inlet, and a gas outlet fluidly coupled to the channel and extending through a bottom surface of the diffusion plate body.

[0011] In yet another embodiment, a processing chamber is provided. The processing chamber includes a processing region and a variable pressure region defined by sidewalls, a chamber base, and a lid structure of the processing chamber,and a gas diffuser coupled to the lid structure including a plug portion disposed in fastening aperture of at least one gas diffuser unit.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of the present disclosure and are therefore not to be considered limiting of its scope, as the present disclosure may admit to other equally effective embodiments.

[0013] Figure 1 illustrates a schematic, cross-sectional view of a processing chamber, according to certain embodiments.

[0014] Figure 2 illustrates a schematic view of a portion of center-supported gas diffuser, according to certain embodiments.

[0015] Figure 3A illustrates a schematic, cross-sectional view of a portion of a diffuser array of the center-supported gas diffuser of Figure 2, according to certain embodiments.

[0016] Figure 3B illustrates a schematic, cross-sectional view of a diffuser of the diffuser array of Figure 3A, according to certain embodiments.

[0017] Figure 3C illustrates a close-up, cross-sectional view of the diffuser of Figure 3B, according to certain embodiments.

[0018] Figure 4A illustrates a schematic, cross-sectional view of a portion of a diffuser array of the center-supported gas diffuser of Figure 2, according to certain embodiments.

[0019] Figure 4B illustrates a schematic, cross-sectional view of a diffuser of the diffuser array of Figure 4A, according to certain embodiments.

[0020] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It iscontemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0021] Embodiments herein are generally directed to semiconductor manufacturing, and more particularly, gas diffusers for substrate processing chambers.

[0022] Center-supported gas diffusers, which are upheld by one or more central rods, are utilized to evenly distribute gases across sizable areas. They function by drawing gas from a central supply line and releasing it through nozzles arranged around the central rod(s). They offer advantages over alternative distribution methods, ensuring precise gas release and simplified maintenance.

[0023] In substrate processing chambers, center-supported gas diffusers (CSDs) may be used to achieve uniform environments for substrate processing. CSDs are secured to the processing chamber, such as to the lid, by fasteners. However, the fasteners and fastener holes in the CSDs generate particles during operation of the processing chamber that may fall into the processing volume through the fastener holes. The embodiments of the present disclosure solve this issue by sealing the fastener holes in the CSD.

[0024] Figure 1 is a schematic side cross-sectional view of one embodiment of a processing chamber 100 of a substrate processing system. The processing chamber 100 is suitable for plasma enhanced chemical vapor deposition (PECVD) processes for fabricating circuitry on a large area substrate 105 made of glass, a polymer, or other suitable substrate. The processing chamber 100 is configured to form structures and devices on the large area substrate 105 for use in the fabrication of liquid crystal displays (LCD’s) or flat panel displays, photovoltaic devices for solar cell arrays, or other structures. The structures may be a plurality of back channel etch inverted staggered (bottom gate) thin film transistors which may comprise a plurality of sequential deposition and masking steps. Other structures may include p-n junctions to form diodes for photovoltaic cells.

[0025] The processing chamber 100 includes a chamber sidewall 110, a bottom 115, and a substrate support 120, such as a susceptor, which supports the large area substrate 105 during processing. A center-supported gas diffuser 145 is positioned opposite the substrate support 120 and the large area substrate 105. The processing chamber 100 also has a port 125, such as a slit valve, that facilitates transfer of and deposition processes on the large area substrate 105 by selectively opening and closing. The processing chamber 100 also includes a lid structure 130, a backing plate 140, and the center-supported gas diffuser 145. In one embodiment, the lid structure 130 supports the backing plate 140 and the center-supported gas diffuser 145. In one embodiment, an interior surface 146 of the backing plate 140 and an interior surface 147 of the chamber sidewall 110 bounds a variable pressure region 148. In one aspect, the processing chamber 100 comprises a body which includes the chamber sidewall 110, the bottom 115 and the backing plate 140 bounding the variable pressure region 148. The backing plate 140 is sealed on its perimeter by suitable O-rings at interfaces where the backing plate 140 and the lid structure 130 may contact each other. The O-rings facilitate electrical insulation as well as seal the variable pressure region 148 when negative pressure is provided by a vacuum pump coupled to the processing chamber 100.

[0026] In one embodiment, the center-supported gas diffuser 145 is supported by the backing plate 140 at a central region thereof by one or more center support members 150. The one or more center support members 150 facilitate support of the center-supported gas diffuser 145 at the central region of the center-supported gas diffuser 145 to control the horizontal profile of the center-supported gas diffuser 145 to mitigate the tendency of the center-supported gas diffuser 145 to droop or sag due to one or a combination of heat, gravity and vacuum. The center-supported gas diffuser 145 may also be supported at a perimeter thereof by a flexible suspension 155. The flexible suspension 155 is adapted to support the center-supported gas diffuser 145 from its edges and to allow lateral expansion and contraction of the center-supported gas diffuser 145.

[0027] The processing chamber 100 is coupled to a gas inlet 160 that is coupled to a gas source and a plasma source 165. The plasma source 165 may be a direct current power source, a radio frequency (RF) power source, or a remote plasmasource. The RF power source may be inductively or capacitively coupled to the processing chamber 100. The gas inlet 160 delivers process or cleaning gases from the gas source through a bore 162 to an intermediate region 170 defined between the backing plate 140 and the center-supported gas diffuser 145. In one example of operation, process gases are delivered from the gas source while the interior of the processing chamber 100 has been pumped down to a suitable pressure by the vacuum pump. One or more process gases flow through the gas inlet 160 to the intermediate region 170 defined between the backing plate 140 and the center- supported gas diffuser 145. The one or more process gases then flow from the intermediate region 170 through a plurality of openings or gas passages 175 formed through the center-supported gas diffuser 145 to a processing region 180 defined in an area below the center-supported gas diffuser 145 and above the substrate support 120.

[0028] The large area substrate 105 is raised from a transfer position to the processing region 180 by moving the substrate support 120 toward the center- supported gas diffuser 145. The height of the processing region 180 may be varied as a process parameter based on a spacing between a lower surface of the center- supported gas diffuser 145 and a substrate receiving surface 190 of the substrate support 120. The substrate support 120 may be heated by an integral heater, such as heating coils or a resistive heater coupled to or disposed within the substrate support 120.

[0029] A plasma may be formed in the processing region 180 by the plasma source 165 coupled to the processing chamber 100. The plasma excited gas is deposited thereon to form structures on the large area substrate 105. In one embodiment, the substrate support 120 is at ground potential to facilitate plasma formation in the processing region 180. A plasma may also be formed in the processing chamber 100 by other means, such as a thermally induced plasma. Although the plasma source 165 is shown coupled to the gas inlet 160 in this embodiment, the plasma source 165 may be coupled to the center-supported gas diffuser 145 or other portions of the processing chamber 100.

[0030] The center-supported gas diffuser 145 is made of or coated with an electrically conductive material and is coupled to the plasma source 165 through the gas inlet 160 or other connection so that it may function as a first electrode within the processing chamber 100. The materials chosen for the center-supported gas diffuser 145 may include steel, titanium, aluminum, or combinations thereof, and the surfaces may be polished or anodized. The center-supported gas diffuser 145 may include a first or upper surface 185A and a second or lower surface 185B. In one embodiment, the upper surface 185A and the lower surface 185B are substantially parallel in crosssection. In another embodiment, at least one of the upper surface 185A and the lower surface 185B may be curved in cross-section to define a concave surface. In another embodiment, at least one of the upper surface 185A and the lower surface 185B are curved to define a convex surface. In another embodiment, at least one of the upper surface 185A and the lower surface 185B are non-parallel. In one embodiment, the center-supported gas diffuser 145 may include a thickness or cross-sectional dimension that is thicker at a perimeter and thinner at a center thereof to form a dished or “scooped” lower surface 185B. In this embodiment, at least the upper surface 185A is substantially planar or level. Thus, the thicker cross-sectional dimension at the perimeter of the center-supported gas diffuser 145 relative to the center of the center- supported gas diffuser 145 forms a desired horizontal profile that is concave relative to the horizontal profile of the substrate support 120. In another embodiment, the substrate receiving surface 190 of the substrate support 120 is substantially planar and the lower surface 185B of the center-supported gas diffuser 145 is concave relative to the substrate receiving surface 190.

[0031] Figure 2 illustrates a top view of a portion of a gas diffuser 200. The gas diffuser 200 may be a center-supported gas diffuser (CSD) and includes a diffusion plate body 202 with a diffuser array 204 along an array centerline 206 aligned along the length of the diffusion plate body 202. The diffuser array 204 may also include a plurality of gas inlets 208 distributed between the gas diffuser units 210 that are not in direct fluid communication with the gas diffuser units 210. It is to be noted that only a portion of the gas diffuser 200 is illustrated to show only a single row of the diffuser array 204. The gas diffuser 200 typically includes a diffuser array 204 having multiple rows. Each row of the diffuser array 204 includes a desired number of gas diffuserunits 210. At least one of the gas diffuser units 210 includes a fastening aperture 212, a first gas inlet 214, and a second gas inlet 216. The fastening aperture 212 allows the diffusion plate body 202 to be secured to the processing chamber 100 by a plurality of fasteners (not shown). Each of the first gas inlet 214 and the second gas inlet 216 are separated from the fastening aperture 212 by an inlet distance 218. The first gas inlet 214 is disposed the inlet distance 218 along the array centerline 206 from the fastening aperture 212. The second gas inlet 216 is disposed the inlet distance 218 along the array centerline 206 from the fastening aperture 212 and opposite the first gas inlet 214. In one embodiment, the inlet distance 218 is uniform across the entire diffuser array 204.

[0032] Figures 3A-3C illustrate a gas diffuser 300 according to one embodiment of the present disclosure. Specifically, Figure 3A illustrates a schematic, cross-sectional side view of the gas diffuser 300 (taken across section line A-A from Figure 2). Figure 3B illustrates a close-up, cross-sectional side view of a gas diffuser unit 310 of the gas diffuser 300. Figure 3C illustrates a close-up, cross-sectional view of a unit center axis 330 of the gas diffuser 300. As shown in Figure 3A, the gas diffuser 300 may be a center-supported diffuser and includes a diffusion plate body 302 with a gas diffuser array 304 of a gas diffuser unit 310 spaced evenly throughout. Each gas diffuser unit 310 includes a fastening aperture 312, a first gas inlet 314, and a second gas inlet 316. The fastening aperture 312, the first gas inlet 314, and the second gas inlet 316 open at a top surface 318 of the diffusion plate body 302. The fastening aperture 312 may have an inner surface that is threaded and configured to mate with fasteners (not shown) to secure the diffusion plate body 302 to a processing chamber (Figure 1 ). The first gas inlet 314 and the second gas inlet 316 are fluidly coupled to a Venturi channel 320 and to a gas outlet 322. The gas outlet 322 opens at a bottom surface 324 of the diffusion plate body 302 facing the processing volume (Figure 1 ) and is fluidly coupled to the processing volume.

[0033] As shown in Figure 3B, the first gas inlet 314 and the second gas inlet 316 may include an inlet axis, e.g., a first inlet axis 332 and a second inlet axis 334, extending radially about a unit center axis 330. The first gas inlet 314 may be aligned at a first axis angle 336 defined as the angle between first inlet axis 332 and unit center axis 330. Similarly, the second gas inlet 316 may be aligned at a second axisangle 338 defined as the angle between second inlet axis 334 and unit center axis 330. In one embodiment, the first inlet axis 332 and the second inlet axis 334 are equal. In another embodiment, the first inlet axis 332 and the second inlet axis 334 differ. The fastening aperture 312 includes an aperture depth 312a and is concentrically aligned with the unit center axis 330 and contains an aperture plug 340 at a distal end of the fastening aperture 312. The first gas inlet 314 and the second gas inlet 316 create or form a gas path 326 that flows inward from the top surface 318 to a junction along the unit center axis 330, below the aperture plug 340. The gas path 326 then flows into the Venturi channel 320 and through to the gas outlet 322 to enter the processing volume.

[0034] As shown in Figure 3C, the fastening aperture 312 includes a main diameter 350 for the aperture depth 312a. At the end of the aperture depth 312a, the fastening aperture 312 includes a plug diameter 352 that is smaller than the main diameter 350. The fastening aperture 312 extends through the diffusion plate body 302 into a junction in the gas path 326 with the first gas inlet 314 and the second gas inlet 316. The aperture plug 340 is disposed at the bottom of the aperture depth 312a and secured to the fastening aperture 312 by the smaller plug diameter 352. The aperture plug 340 is made of a material that is inert to processing gases being diffused and may be made of the same material as the diffusion plate body 302. Such materials may include aluminum, stainless steel, or silicon carbide. The aperture plug 340 may include a plug depth 342 that seals the fastening aperture 312 from the gas path 326 created by the first gas inlet 314 and the second gas inlet 316. Further the aperture plug 340 may include plug tapers 344 to facilitate gas flow along the outer surface of the aperture plug 340. The aperture plug 340 may also include a planar bottom surface 346 as shown to reduce interference with the gas path 326. The aperture plug 340 may be coupled to the fastening aperture 312 by any suitable method, including shrink fitting, press fitting, by an adhesive, welding, or a combination thereof. The aperture plug 340 prevents debris and particles from the fastening aperture 312 and associated fastener from entering the gas path 326 created by the first gas inlet 314 and second gas inlet 316, which ultimately prevents contamination of the substrate being processed in the processing volume (not shown).

[0035] Figures 4A and 4B illustrate a gas diffuser 400 according to another embodiment of the present disclosure. Specifically, Figure 4A illustrates a schematic, cross-sectional side view of the gas diffuser 400 (taken across section line A-A from Figure 2). Figure 4B illustrates a close-up, cross-sectional side view of a gas diffuser unit 410 of the gas diffuser 400. Figure 4C illustrates a close-up, cross-sectional view of a unit center axis 430 of the gas diffuser 400. As shown in Figure 4A, the gas diffuser 400 includes a diffusion plate body 402 with a gas diffuser array 404 of gas diffuser unit 410 spaced evenly throughout. Each gas diffuser unit 410 includes a fastening aperture 412, a first gas inlet 414, and a second gas inlet 416. The fastening aperture 412, the first gas inlet 414, and the second gas inlet 416 open at a top surface 418 of the diffusion plate body 402. The first gas inlet 414 and the second gas inlet 416 are fluidly coupled to a Venturi channel 420 and to a gas outlet 422. The gas outlet 422 opens at a bottom surface 424 facing the processing volume (Figure 1 ).

[0036] As shown in Figure 4B, the first gas inlet 414 and the second gas inlet 416 may include an inlet axis, e.g., a first inlet axis 432 and a second inlet axis 434, extending radially about a unit center axis 430. The first gas inlet 414 may be aligned at a first axis angle 436 defined as the angle between first inlet axis 432 and unit center axis 430. Similarly, the second gas inlet 416 may be aligned at a second axis angle 438 defined as the angle between second inlet axis 434 and unit center axis 430. In one embodiment, the first inlet axis 432 and the second inlet axis 434 are equal. In another embodiment, the first inlet axis 432 and the second inlet axis 434 differ. The fastening aperture 412 includes an aperture depth 412a that is concentrically aligned with the unit center axis 430 and contains a plug portion 440 at the distal end of the fastening aperture 412. The first gas inlet 414 and the second gas inlet 416 create or form a gas path 426 that flows inward from the top surface 418 to a junction along the unit center axis 430, below the plug portion 440. The gas path 426 then flows into the Venturi channel 420 and through to the gas outlet 422 to enter the processing volume.

[0037] The fastening aperture 412 includes a main diameter 450 that extends for the aperture depth 412a. The plug portion 440 is concentrically aligned with the unit center axis 430 and is continuous with the diffusion plate body 402, e.g., the plug portion 440 is part of the diffusion plate body 402. The plug portion 440 includes aplug depth 442 that is defined by the end of the aperture depth 412a and the gas path 426 created by the first gas inlet 414 and the second gas inlet 416. The plug portion 440 includes a plurality of plug tapers 444 that are continuous with the first gas inlet 414 and the second gas inlet 416. This configuration allows the fastening aperture 412 to act as a blind hole in the diffusion plate body 402 which couples to a fastener (not shown) to secure the gas diffuser 400 to a processing chamber (not shown). The plug portion 440 prevents debris and particles from the fastening aperture 412 and associated fastener from entering the gas path 426 created by the first gas inlet 414 and second gas inlet 416, which ultimately prevents contamination of the substrate being processed in the processing volume (not shown).

[0038] The present disclosure provides a center-supported gas diffuser for use in a substrate processing chamber. The gas diffuser prevents fasteners from directly threading into the gas path of the diffuser by adding a plug or plug portion at the bottom of the fastener apertures to seal off particles generated from the interaction of the threading. The seal created by the plug of the present disclosure prevents particle contamination from entering the gas path and flowing onto a substrate in the processing volume.

[0039] When introducing elements of the present disclosure or exemplary aspects or embodiments thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements.

[0040] The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0041] The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, the objects A and C may still be considered coupled to one another — even if objects A and C do not directly physically touch each other. For instance, a fist object may be coupled to a second object even though the first object is never directly in physical contact with the second object.

Claims

What is claimed is:1 . A gas diffuser, comprising: a diffusion plate body; and a diffuser array in the diffusion plate body and comprising at least one gas diffuser unit, the gas diffuser unit comprising: a fastening aperture through a top surface of the diffusion plate body; a first gas inlet disposed an inlet distance from the fastening aperture; a second gas inlet disposed the inlet distance from the fastening aperture and opposite the first gas inlet; an aperture plug at a distal end of the fastening aperture; a channel fluidly coupled to the first gas inlet and the second gas inlet; and a gas outlet fluidly coupled to the channel and extending through a bottom surface of the diffusion plate body.

2. The gas diffuser of claim 1 , wherein the fastening aperture includes a main diameter and a plug diameter that is smaller than the main diameter.

3. The gas diffuser of claim 2, wherein the aperture plug is disposed in the plug diameter.

4. The gas diffuser of claim 1 , wherein the aperture plug comprises a material configured to be inert to processing gases flowed through the first gas inlet and the second gas inlet.

5. The gas diffuser of claim 1 , wherein the aperture plug comprises plug tapers along the first gas inlet and the second gas inlet.

6. The gas diffuser of claim 1 , wherein the aperture plug is disposed at an aperture depth of the fastening aperture.

7. The gas diffuser of claim 1 , wherein the aperture plug is configured to seal the fastening aperture from a gas path formed by the first gas inlet and the second gas inlet.

8. A gas diffuser, comprising: a diffusion plate body; and a diffuser array in the diffusion plate body and comprising at least one gas diffuser unit, the gas diffuser unit comprising: a fastening aperture through a top surface of the diffusion plate body; a first gas inlet disposed an inlet distance from the fastening aperture; a second gas inlet disposed the inlet distance from the fastening aperture and opposite the first gas inlet; a plug portion at a distal end of the fastening aperture; a channel fluidly coupled to the first gas inlet and the second gas inlet; and a gas outlet fluidly coupled to the channel and extending through a bottom surface of the diffusion plate body.

9. The gas diffuser of claim 8, wherein the plug portion and the diffusion plate body are continuous.

10. The gas diffuser of claim 8, wherein the plug portion comprises a plug depth configured to seal the fastening aperture from the first gas inlet and the second gas inlet.

11. The gas diffuser of claim 8, wherein the plug portion comprises plug tapers along the first gas inlet and the second gas inlet.

12. The gas diffuser of claim 8, wherein the plug portion is concentrically aligned with a unit center axis of the gas diffuser unit.

13. The gas diffuser of claim 8, wherein the plug portion is disposed at an aperture depth of the fastening aperture.

14. The gas diffuser of claim 8, wherein the first gas inlet is at a first axis angle from a unit center axis, the second gas inlet is at a second axis angle from the unit center axis, and the first axis angle and the second axis angle are equal.

15. A processing chamber, comprising:a processing region and a variable pressure region defined by sidewalls, a chamber base, and a lid structure of the processing chamber; and a gas diffuser coupled to the lid structure comprising a plug portion disposed in a fastening aperture of at least one gas diffuser unit.

16. The processing chamber of claim 15, wherein the plug portion and a diffusion plate body of the gas diffuser are continuous.

17. The processing chamber of claim 15, wherein the plug portion comprises a plug depth configured to seal the fastening aperture from a first gas inlet and a second gas inlet.

18. The processing chamber of claim 15, wherein the plug portion is concentrically aligned with a unit center axis of the at least one gas diffuser unit.

19. The processing chamber of claim 15, wherein the plug portion is disposed at an aperture depth of the fastening aperture.

20. The processing chamber of claim 15, wherein the plug portion comprises plug tapers along a first gas inlet and a second gas inlet.

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