KR20210006019A - Temperature controlled gas diffuser for flat panel process equipment - Google Patents

Abstract

Embodiments described herein provide gas distribution assemblies that improve the uniformity of films to be deposited or to be etched. One embodiment of gas distribution assemblies includes a diffuser having a top diffuser plate and a plurality of first gas passage sections disposed in the top diffuser plate. Each first gas passage section is adjacent to at least one fluid channel disposed in the top diffuser plate. Each fluid channel is connected to a supply channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with the fluid supply conduit of the heat exchanger. Each fluid channel is connected to a return channel disposed on the top diffuser plate. The return channel has a return outlet configured to be coupleable with the fluid return conduit of the heat exchanger. The lowermost diffuser plate is coupled to the uppermost diffuser plate.

Description

Temperature controlled gas diffuser for flat panel process equipment

[0001] Embodiments of the present disclosure generally relate to process chambers, such as plasma-enhanced chemical vapor deposition (PECVD) chambers. More specifically, embodiments of the present disclosure relate to gas distribution assemblies for process chambers.

[0002] Chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) are generally used to deposit thin films on a substrate, such as a transparent substrate for a semiconductor wafer or flat panel display. CVD and PECVD are generally achieved by introducing a precursor gas or gas mixture into a vacuum chamber containing the substrate. The precursor gas or gas mixture is typically directed downwards through a gas diffuser located near the top of the chamber. The diffuser plate is placed a short distance above the substrate positioned on the heated substrate support, so that the diffuser and precursor gas or gas mixture are heated by radiated heat from the substrate support. During PECVD, the precursor gas or gas mixture in the chamber is energized (eg, excited) into a plasma by applying RF power to the chamber from one or more radio frequency (RF) sources coupled to the chamber. The excited gas or gas mixture reacts to form a layer of material on the surface of the substrate positioned on the heated substrate support. Volatile by-products produced during the reaction are pumped out of the chamber through an exhaust system.

[0003] Flat panels processed by CVD and PECVD processing are typically large, and usually exceed 370 mm x 470 mm. Thus, large gas diffuser plates (or gas distribution plates) that are relatively large in size compared to gas diffuser plates utilized in processing 200 mm and 300 mm semiconductor wafers, in particular, to provide a uniform process gas flow over flat panels. Is utilized. Since the gas diffuser plates are large and heated only by the excited plasma and radiant heat from the substrate support, the temperature distribution of the gas diffuser plates is not uniform, and the deposition of films with non-uniform thicknesses or non-uniform etching of the films. Results.

[0004] Accordingly, there is a need for improved gas distribution assemblies that improve the uniformity of films to be deposited or films to be etched.

[0005] In one embodiment, a diffuser is provided. The diffuser includes a top diffuser plate having an upstream surface and a downstream surface, and a plurality of first gas passage sections disposed in the top diffuser plate. Each first gas passage is adjacent to at least one fluid channel disposed in the top diffuser plate. Each fluid channel is connected to a supply channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with the fluid supply conduit of the heat exchanger. Each fluid channel is connected to a return channel disposed on the top diffuser plate. The return channel has a return outlet configured to be coupleable with the fluid return conduit of the heat exchanger. The lowermost diffuser plate is coupled to the uppermost diffuser plate. The lowermost diffuser plate has an upstream surface and a downstream surface.

[0006] In another embodiment, a diffuser is provided. The diffuser includes a top diffuser plate having an upstream surface and a downstream surface, and a plurality of first gas passage sections disposed in the top diffuser plate. Each first gas passage is adjacent to at least one fluid channel disposed in the top diffuser plate. Each fluid channel is connected to one of a supply channel and a supply bypass channel disposed in the top diffuser plate. The supply channel has a supply inlet configured to be coupleable with the fluid supply conduit of the heat exchanger. The supply bypass channel is in fluid communication with the supply channel. Each fluid channel is connected to one of a return channel and a return bypass channel disposed on the top diffuser plate. The return channel has a return outlet configured to be coupleable with the fluid return conduit of the heat exchanger. The return bypass channel is in fluid communication with the return channel. The lowermost diffuser plate is coupled to the uppermost diffuser plate. The lowermost diffuser plate has an upstream surface and a downstream surface.

[0007] In yet another embodiment, a chamber is provided. The chamber includes a support assembly and a radio frequency (RF) power source coupled to the diffuser. The diffuser is disposed opposite the support assembly. The diffuser includes a top diffuser plate having an upstream surface and a downstream surface, and a plurality of first gas passage sections disposed in the top diffuser plate. Each first gas passage is adjacent to at least one fluid channel disposed in the top diffuser plate. Each fluid channel is connected to a supply channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with the fluid supply conduit of the heat exchanger. Each fluid channel is connected to a return channel disposed on the top diffuser plate. The return channel has a return outlet configured to be coupleable with the fluid return conduit of the heat exchanger. The lowermost diffuser plate is coupled to the uppermost diffuser plate. The lowermost diffuser plate has an upstream surface and a downstream surface.

[0008] In such a way that the above-listed features of the present disclosure can be understood in detail, a more specific description of the present disclosure briefly summarized above may be made with reference to embodiments, some of which are attached It is illustrated in the drawings. However, it should be noted that the appended drawings are merely illustrative of exemplary embodiments and should not be regarded as limiting the scope of the present disclosure, and that other equally effective embodiments may be accepted.
1 is a schematic cross-sectional view of an embodiment of a plasma enhanced chemical vapor deposition system according to the embodiment.
2A is a partial schematic cross-sectional view of an exemplary diffuser according to an embodiment, and FIG. 2B is a bottom cross-sectional view of the exemplary diffuser.
2C is a negative bottom perspective view of a top diffuser plate according to an embodiment.
[0012] Figure 2D is an enlarged negative section of the top diffuser plate according to an embodiment.
2E is a negative bottom perspective view of a top diffuser plate according to an embodiment.
2F is an enlarged negative section of a top diffuser plate according to an embodiment.
[0015] To facilitate understanding, the same reference numbers have been used where possible to designate the same elements common to the drawings. It is contemplated that elements and features of one embodiment may be beneficially included in other embodiments without further description.

[0016] Embodiments described herein provide gas distribution assemblies that improve the uniformity of films to be deposited or to be etched. Each of the gas distribution assemblies includes one of a one-way flow and a two-way flow of fluid through the diffuser, whereby excess heat is removed and/or heat is provided to the diffuser to maintain a predetermined diffuser temperature. Maintaining the diffuser 105 at a predetermined diffuser temperature independent of the intensity of the plasma during processing and the heat radiated from the substrate support produces a deposited or etched film with improved uniformity.

[0017] 1 is a schematic cross-sectional view of one embodiment of a plasma enhanced chemical vapor deposition (PECVD) chamber 100, which is available from Applied Materials, Inc. located in Santa Clara, California. It is understood that the system described below is an exemplary chamber, and that other chambers, including chambers from other manufacturers, may be used with aspects of the disclosure or may be modified to achieve aspects of the disclosure. Should be. Chamber 100 includes a chamber body 102, a substrate support assembly 104, and a gas distribution assembly 106. The gas distribution assembly 106 is positioned opposite the substrate support assembly 104 and a process volume 108 is defined between them.

[0018] The substrate support assembly 104 is disposed at least partially within the chamber body 102. The substrate support assembly 104 supports the substrate 110 during processing. The substrate support assembly 104 includes a substrate support 112. The substrate support 112 has a lower surface 114 for mounting the stem 118 and an upper surface 116 for supporting the substrate 110. The stem 118 couples the substrate support assembly 104 to the lift system 120, the lift system 120 to the chamber 100 and into the chamber 100 through the slit valve 122 of the chamber body 102. Move the substrate support assembly 104 between a transfer position and a processing position (as shown) to enable transfer of the substrate from ).

[0019] In one embodiment, which may be combined with other embodiments described herein, resistive elements (not shown) disposed on the substrate support are coupled to a supply that controllably heats the substrate support 112, such as a power source. do. In another embodiment that may be combined with other embodiments described herein, at least one fluid channel (not shown) is connected to the heat exchanger 124, and the heat exchanger 124 is an inlet of at least one fluid channel. Is connected to the at least one fluid channel through a support supply conduit 126 connected to and through a support return conduit 128 connected to the outlet of the at least one fluid channel. The heat exchanger 124 circulates the fluid through the substrate support 112 so that excess heat is removed and/or heat is provided to the substrate support 112 to maintain a predetermined support temperature. The predetermined support temperature may be set to a constant temperature based on the process parameters so that a uniform temperature distribution of the substrate 110 is maintained regardless of the intensity of the plasma during processing. The fluid may include a material capable of maintaining a temperature between about 50 degrees Celsius and about 450 degrees Celsius.

[0020] The gas distribution assembly 106 includes a diffuser 105 suspended from a backing plate 103 by a hanger plate 107. A plurality of gas passages 109 are formed through the diffuser 105 in order to allow a uniform predetermined distribution of gas to pass through the diffuser 105 and into the process volume 108. The hanger plate 107 maintains the diffuser 105 and the backing plate 103 in a spaced relationship to define a plenum 111 between the diffuser 105 and the backing plate 103. The backing plate 103 includes a gas inlet passage 113 coupled to a manifold 115 coupleable to one or more gas sources 117. The plenum 111 allows gases to be uniformly provided over the diffuser 105 and flow in a uniform distribution through the plurality of gas passages 109 over the width of the gas distribution assembly 106. This allows the gas to flow evenly in the process volume 108.

[0021] The gas distribution assembly 106 is coupled to a radio frequency (RF) power source 119 and the RF power source 119 is used to generate a plasma for processing of the substrate 110. In general, the substrate support assembly 104 is such that RF power is supplied to the gas distribution assembly 106 by the RF power source 119 to provide a capacitive coupling between the diffuser 105 and the substrate support 112. Grounded. When RF power is supplied to the diffuser 105, an electric field is created between the diffuser 105 and the substrate support 112, and thus the process volume 108 between the substrate support 112 and the diffuser 105. The atoms of the existing gases are ionized and emit electrons. During processing, the heat from the substrate support 112 radiated to the diffuser 105 and the heat generated from the intensity of the plasma may be non-uniform, and thus hot and cold across the diffuser 105 ( cold) zones can be created. The gas distribution assembly 106 includes a system 101 to maintain a uniform predetermined diffuser temperature across the diffuser 105 regardless of the intensity of the heat radiated from the substrate support 112 and the plasma during processing. do. Maintaining the diffuser 105 at a predetermined diffuser temperature regardless of the heat radiated from the substrate support 112 and the intensity of the plasma during processing produces a deposited or etched film with improved uniformity.

[0022] System 101 includes at least a plurality of fluid channels 121. Each of the fluid channels 121 is a channel inlet (Fig. 2C to Fig. 2F) coupled to at least one of a supply channel (shown in Figs. 2C to 2F) and a supply bypass channel (shown in Figs. 2E and 2F). Shown in). Each of the fluid channels 121 is a channel outlet (Fig. 2C to Fig. 2F) coupled to at least one of a return channel (shown in Figs. 2C to 2F) and a return bypass channel (Fig. 2E and Fig. 2F). Shown in). The heat exchanger 123 is connected to the supply channel through a fluid supply conduit 125 connected to the inlet of the supply channel (shown in FIGS. 2C and 2E). The heat exchanger 123 is connected to the return channel through a fluid return conduit 127 connected to the outlet of the return channel (shown in FIGS. 2C and 2E). Heat exchanger 123 circulates fluid through fluid channels 121, whereby excess heat is removed and/or heat is provided to diffuser 105 to maintain a predetermined diffuser temperature. The predetermined diffuser temperature may be set to a constant temperature based on the process parameters so that a uniform temperature distribution of the diffuser 105 is maintained regardless of the intensity of the heat radiated from the substrate support 112 and the plasma during processing. have. The fluid may include a material capable of maintaining a temperature between about 50 degrees Celsius and about 450 degrees Celsius.

[0023] A controller 130 is coupled to the chamber 100 and is configured to control aspects of the chamber 100 during processing. The controller 130 may include a central processing unit (CPU) (not shown), a memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any type of computer processors used in industrial sites to control various processes and hardware (e.g., motors and other hardware) and monitor processes (e.g., fluid flows). have. Memory (not shown) is connected to the CPU, and is readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage locally or remotely. It may be one or more of. Software instructions and data may be coded and stored in memory to instruct the CPU. Further, support circuits (not shown) are connected to the CPU to support the processor in a conventional manner. Support circuits may include conventional cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by controller 130 determines which tasks can be performed by chamber 100. The program may be software readable by controller 130 and may include instructions for monitoring and controlling a predetermined diffuser temperature of diffuser 105, for example.

[0024] 2A is a schematic partial cross-sectional view of an exemplary diffuser 105 and FIG. 2B is a bottom cross-sectional view of an exemplary diffuser 105. The diffuser 105 is configured with a thickness 242 that maintains sufficient flatness across the hanger plate 107 so as not to adversely affect substrate processing. In one embodiment that may be combined with other embodiments described herein, the thickness 242 of the diffuser 105 is between about 0.8 inches and about 2.0 inches. The diffuser 105 may be circular for semiconductor wafer fabrication, or polygonal, such as rectangular, for flat panel display fabrication.

[0025] The diffuser 105 consists of an uppermost diffuser plate 202, which includes an upstream surface 206 and a downstream surface 208 facing the backing plate 103. In one embodiment, which can be combined with other embodiments described herein, the downstream surface 208 of the diffuser 105 is cast, brazed, against the upstream surface 210 of the lowermost diffuser plate 204 ( brazed), forged, hot iso-statically pressed, and sintered, the lowermost diffuser plate 204 comprising a downstream surface 212 facing the substrate support 112 do. The uppermost diffuser plate 202 has a thickness 244 and the lowermost diffuser plate 204 has a thickness 246. Each gas passage 109 includes a first gas passage section 248 in the upper diffuser plate 202 and a second passage section 250 in the lower diffuser plate 204. In one embodiment that may be combined with other embodiments described herein, each of the fluid channels 121 adjacent to the orifice hole 216 is spaced a distance 240 from the orifice hole 216 . In another embodiment that may be combined with other embodiments described herein, each of the fluid channels 121 has a width 238 and a height 236. In another embodiment that may be combined with other embodiments described herein, each of the fluid channels 121 is U-shaped or V-shaped.

[0026] A negative bottom perspective view of the top diffuser plate 202 of the exemplary diffuser 105 is shown in FIG. 2C, an enlarged negative section of the top diffuser plate 202 is shown in FIG. 2D, and each of the fluid channels 121 It is disposed adjacent to at least one first gas passage section 248. Fluid channels 121 are formed on the downstream surface 208 of the top diffuser plate 202. Each first gas passage section 248 is disposed on the top diffuser plate 202. As shown in FIG. 2A, each first gas passage section 248 is defined by a first bore 214 coupled to an orifice hole 216, and each second passage section 250 ) Is defined in the lowermost diffuser plate 204 by a second bore 218 coupled to an orifice hole 216 in the uppermost diffuser plate 202. In the embodiment shown in FIGS. 2C and 2D having a unidirectional flow configuration, each of the fluid channels 121 is coupled to a channel inlet 213 coupled to a supply channel 207 and a return channel 209. It has a channel outlet 215. The supply channel 207 includes an inlet 203 to be connected to the heat exchanger 123 through a fluid supply conduit 125, and an outlet 205 to be connected to the heat exchanger 123 through a fluid return conduit 127. Heat exchanger 123 circulates fluid through fluid channels 121 in a one-way flow to maintain diffuser 105 at a predetermined diffuser temperature. In one embodiment that may be combined with other embodiments described herein, system 101 includes a plurality of thermocouples 251 coupled to controller 130 to determine the temperature of diffuser 105. do. The controller 130 coupled to the heat exchanger 123 and the thermocouples 251 is operable to monitor and control the temperature and circulation of fluid entering the supply channel 207.

[0027] First bore 214, orifice hole 216, and second bore 218 are combined to form a path through diffuser 105. The first bore 214 extends from the upstream surface 206 of the top diffuser plate 202 to the bottom 220 by a first length 230. The lowermost portion 220 of the first bore 214 is tapered, beveled, and chamfered to minimize flow restriction when gases flow from the first bore 214 into the orifice hole 216. It may be chamfered or circular. The first bore 214 generally has a diameter of about 0.093 inches to about 0.218 inches, and in one embodiment about 0.156 inches.

[0028] A second bore 218 is formed in the lowermost diffuser plate 204 and extends from the downstream surface 212 to a third length 234 of about 0.10 inches to about 2.0 inches. Preferably, the third length 234 is between about 0.1 inches and about 1.0 inches. The diameter 226 of the second bore 218 is generally about 0.1 inches to about 1.0 inches, and may be spread at an angle 224 of about 10 degrees to about 50 degrees. Preferably, the diameter 226 is between about 0.1 inches and about 0.5 inches, and the angle 224 is between 20 degrees and about 40 degrees. The diameter 226 of the second bore 218 refers to the diameter that intersects the downstream surface 212. The surface area of the second bore 218 is about 0.05 square inches to about 10 square inches, and preferably about 0.05 square inches to about 5 square inches.

[0029] An example of a diffuser 105 used to process 1500 mm x 1850 mm substrates has a diameter 226 of 0.250 inches and second bores 218 at an angle 224 of about 22 degrees. The distance 228 between the rims 252 of adjacent second bores 218 is between about 0 inches and about 0.6 inches, preferably between about 0 inches and about 0.4 inches. The diameter 254 of the first bore 214 is generally at least less than, but not limited to, the diameter 226 of the second bore 218. The lowermost portion 222 of the second bore 218 may be tapered, beveled, chamfered, or circular in order to minimize pressure loss of gases flowing out of the orifice hole 216 into the second bore 218. .

[0030] The orifice hole 216 generally couples the lowermost portion 220 of the first bore 214 and the lowermost portion 222 of the second bore 218. The orifice hole 216 generally has a diameter of about 0.01 inches to about 0.3 inches, preferably about 0.01 inches to about 0.1 inches, and is typically about 0.02 inches to about 1.0 inches, preferably about 0.02 inches to It has a second length 232 of about 0.5 inches. The second length 232 and diameter (or other geometrical properties) of the orifice hole 216 facilitates a uniform distribution of gas over the upstream surface 206 of the top diffuser plate 202. ) Is the main cause of back pressure. The orifice hole 216 is typically configured uniformly between the plurality of gas passages 109, but the restriction through the orifice hole 216 is one area of the diffuser 105 compared to the other area of the diffuser 105. It may be configured differently between the plurality of gas passages 109 to facilitate more gas flow through. For example, the orifice hole 216 is closer to the walls of the chamber body 102 to allow more gas to flow through the edges of the diffuser 105 to increase the deposition rate around the substrate 110. , May have a larger diameter and/or a shorter second length 232 in such gas passages 109 of the diffuser 105. The thickness of the diffuser plate is from about 0.8 inches to about 3.0 inches, preferably from about 0.8 inches to about 2.0 inches.

[0031] A negative bottom perspective view of the top diffuser plate 202 having a bidirectional flow configuration is shown in FIG. 2E and an enlarged negative section is shown in FIG. 2F. The bidirectional flow configuration includes a first portion of a plurality of fluid channels 121, wherein the first portion of the plurality of fluid channels 121 has channel inlets 211 coupled to the supply channel 207, and It has channel outlets 249 coupled to the return channel 209. The bidirectional flow configuration includes a second portion of a plurality of fluid channels 121, and a second portion of the plurality of fluid channels 121 has channel inlets 211 coupled to the supply bypass channel 217 , And channel outlets 249 coupled to the return bypass channel 219. Supply bypass channel 217 is coupled to supply channel 207 by supply delivery channels 221. Return bypass channel 219 is coupled to return channel 209 by return transfer channels 223. The fluid channels 121 of the first portion and the second portion alternate for bidirectional flow of the fluid. The heat exchanger 123 supplies fluid through a supply channel 207, a first portion of the plurality of fluid channels 121, and a return channel 209, and a supply bypass channel 217, a plurality of fluid channels. Cycling through a second portion of 121, and return bypass channel 219, maintains diffuser 105 at a predetermined diffuser temperature.

[0032] In summary, gas distribution assemblies are described herein that improve the uniformity of films to be deposited or films to be etched. Each of the gas distribution assemblies includes one of a one-way flow and a two-way flow of fluid through the diffuser, whereby excess heat is removed and/or heat is provided to the diffuser to maintain a predetermined diffuser temperature. Maintaining the diffuser at a predetermined diffuser temperature irrespective of the intensity of the plasma during processing and the heat radiated from the substrate support produces a deposited or etched film with improved uniformity.

[0033] While the foregoing relates to examples of the present disclosure, other and additional examples of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the following claims. .

Claims (15)

A top diffuser plate having an upstream surface and a downstream surface;
A plurality of first gas passage sections disposed in the top diffuser plate, each first gas passage section being adjacent to at least one fluid channel disposed in the top diffuser plate,
Each fluid channel is connected to a supply channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with a fluid supply conduit of the heat exchanger,
Each fluid channel is connected to a return channel disposed in the top diffuser plate, the return channel having a return outlet configured to be coupleable with a fluid return conduit of the heat exchanger; And
A bottom diffuser plate coupled to the top diffuser plate
Including,
The lowermost diffuser plate has an upstream surface and a downstream surface,
Diffuser. The method of claim 1,
Each first gas passage section includes a first bore coupled to an orifice hole, and each second gas passage section is a second gas passage section coupled to the orifice hole of the top diffuser plate. Including bore,
Diffuser. The method of claim 2,
Each orifice hole is adjacent to at least one fluid channel disposed in the top diffuser plate,
Diffuser. The method of claim 3,
Each fluid channel adjacent to the orifice hole is spaced a first distance from the orifice hole,
Diffuser. The method of claim 1,
The heat exchanger, when coupled with the supply channel and the return channel, circulates fluid from the fluid supply conduit to the heat exchanger through the supply channel, each fluid channel, the return channel, and the fluid return conduit. Operable to let,
Diffuser. The method of claim 5,
A controller coupled to the heat exchanger is operable to control circulation of the fluid to maintain a predetermined diffuser temperature,
Diffuser. The method of claim 6,
Thermocouples disposed on the top diffuser plate are coupled to the controller,
Diffuser. The method of claim 1,
The downstream surface of the uppermost diffuser plate is at least one of cast, brazed, forged, hot iso-statically pressed, and sintered against the upstream surface of the lowermost diffuser plate. Made,
Diffuser. The method of claim 1,
The diffuser is disposed in the processing chamber opposite a substrate support disposed in the processing chamber,
Diffuser. A top diffuser plate having an upstream surface and a downstream surface;
A plurality of first gas passage sections disposed in the top diffuser plate, each first gas passage section being adjacent to at least one fluid channel disposed in the top diffuser plate,
Each fluid channel is connected to one of a supply channel and a supply bypass channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with the fluid supply conduit of the heat exchanger. , The supply bypass channel is in fluid communication with the supply channel,
Each fluid channel is connected to one of a return channel and a return bypass channel disposed on the top diffuser plate, the return channel having a return outlet configured to be coupled to the fluid return conduit of the heat exchanger, and the return bypass The pass channel is in fluid communication with the return channel; And
A bottom diffuser plate coupled to the top diffuser plate
Including,
The lowermost diffuser plate has an upstream surface and a downstream surface,
Diffuser. Support assembly; And
A radio frequency (RF) power source coupled to a diffuser
Including,
The diffuser is disposed opposite the support assembly,
The diffuser,
A top diffuser plate having an upstream surface and a downstream surface;
A plurality of first gas passage sections disposed in the top diffuser plate, each first gas passage section being adjacent to at least one fluid channel disposed in the top diffuser plate,
Each fluid channel is connected to a supply channel disposed in the top diffuser plate, the supply channel having a supply inlet configured to be coupleable with a fluid supply conduit of the heat exchanger,
Each fluid channel is connected to a return channel disposed in the top diffuser plate, the return channel having a return outlet configured to be coupleable with a fluid return conduit of the heat exchanger; And
A bottom diffuser plate coupled to the top diffuser plate
Including,
The lowermost diffuser plate has an upstream surface and a downstream surface,
chamber. The method of claim 11,
The heat exchanger, when coupled with the supply channel and the return channel, circulates fluid from the fluid supply conduit to the heat exchanger through the supply channel, each fluid channel, the return channel, and the fluid return conduit. Operable to let,
chamber. The method of claim 12,
A controller coupled to the heat exchanger is operable to control circulation of the fluid to maintain a predetermined diffuser temperature,
chamber. The method of claim 13,
Thermocouples disposed on the top diffuser plate are coupled to the controller,
chamber. The method of claim 11,
The downstream surface of the uppermost diffuser plate is made of at least one of being cast, brazed, forged, hot isostatically formed, and sintered to the upstream surface of the lowermost diffuser plate,
chamber.

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