CN101144154B - Plasma uniformity control by gas diffuser hole design - Google Patents

Abstract

The present invention is an example of a gas diffusion plate for distributing gases in a plasma processing chamber. The gas distribution plate includes a diffuser plate having an upstream side and a downstream side, and a plurality of gas passages passing between the upstream side and the downstream side of the diffuser plate. The gas passages include a hollow cathode cavity located on the downstream side to enhance plasma ionization. The depth, diameter, surface area and density of the hollow cathode cavity extending to the downstream side of the gas channel can be gradually increased from the center of the diffusion plate to the edge, so as to improve the thickness and property uniformity of the film layer on the substrate. The increasing depth, diameter, surface area and density from the center of the diffuser towards the edges can be achieved by bending the diffuser towards the downstream side and then smoothing the curvature of the downstream side. The bending of the diffuser plate can also be achieved by a heat treatment or a vacuum process. The depth, diameter, surface area and density gradually increasing from the center to the edge of the diffusion plate can also be achieved through the grinding process controlled by computer numerical control. The diffuser plate shown having the depth, diameter and surface area of the hollow cathode cavity gradually increases from the center to the edge of the diffuser plate, resulting in improved, uniform film thickness and film properties.

Description

Plasma Uniformity Control Using Gas Diffusion Plate Channel Design

The present application is a divisional application of the invention patent application submitted by the applicant on December 31, 2004, with the application number 200410082199.3 and the title of the invention "Plasma Uniformity Control Using Gas Diffusion Plate Channel Design".

technical field

Embodiments of the invention generally relate to a gas distribution plate assembly and methods of distributing gases in a process chamber.

Background technique

Liquid crystal displays or flat panel displays are commonly used in active matrix displays such as computer and television screens. Moreover, the film layer is usually deposited on a substrate (such as a transparent substrate for a flat panel display or a semiconductor wafer) by a plasma-enhanced chemical vapor deposition process (PECVD). PECVD is generally accomplished by introducing a precursor gas or gas mixture into a vacuum chamber containing a substrate. The precursor gas or gas mixture is typically directed down through a gas distribution plate near the top of the vacuum chamber. RF power is applied to the vacuum chamber from one or more radio frequency (RF) power sources coupled to the vacuum chamber to excite a precursor gas or gas mixture in the vacuum chamber into a plasma. The excited gas or gas mixture reacts to form a layer of substance on the substrate surface on a substrate support column controlled by a temperature. Volatile by-products during the reaction are exhausted from the vacuum chamber through an exhaust system.

Flat panels processed by PECVD technology are generally large flat panels, whose dimensions often exceed 370 mm x 470 mm. In the future, large-area substrates exceeding 4 square meters will appear. Gas distribution plates used to provide uniform process gas flow across the flat plate are generally of large area, especially when compared to gas distribution plates used to process 200 mm and 300 mm semiconductor wafers.

As the size of the substrate in the TFT-LCD industry continues to increase, it has become an important issue to control the film thickness and film property uniformity in the large-area plasma-enhanced chemical vapor deposition chamber. TFT is a type of flat panel display. Differences in deposition rate and/or film properties, such as film stress, between the center of the substrate and the edge of the substrate will become apparent.

Therefore, there is an urgent need for an improved gas distribution plate assembly that can improve the uniformity of film deposition thickness and film properties.

Contents of the invention

The present invention provides a gas distribution plate for distributing gases in a process chamber. In one embodiment, a gas distribution plate assembly for a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; and an inner gas channel and an outer gas channel passing through the The diffuser plate contains hollow cathode cavities between and on the downstream side, wherein the inner gas passages have a lower volume density of the hollow cathode cavities than the outer gas passages.

In another embodiment, a gas distribution plate for a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; and an inner gas channel and an outer gas channel through the diffuser plate. The plate contains hollow cathode cavities between and on the downstream side, wherein the hollow cathode cavities of the inner gas channels have a lower surface area density than the hollow cathode cavities of the outer gas channels.

In another embodiment, a gas distribution plate for a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; and a plurality of gas channels passing through the diffuser plate upstream and downstream Between the sides and on the downstream side there are hollow cathode cavities, wherein the density of the hollow cathode cavities gradually increases from the center to the edge of the diffuser plate.

In another embodiment, a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; inner gas channels and outer gas channels passing through the upstream side and the downstream side of the diffuser plate comprising hollow cathode cavities between and on the downstream side, wherein the volume density of the hollow cathode cavities of the inner gas passages is lower than the volume density of the hollow cathode cavities of the outer gas passages; and a substrate support adjacent to the downstream side of the diffuser plate column.

In another embodiment, a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; inner gas channels and outer gas channels passing through the upstream side and the downstream side of the diffuser plate comprising hollow cathode cavities between and on the downstream side, wherein the hollow cathode cavities of the inner gas passages have a lower surface area density than the hollow cathode cavities of the outer gas passages; and a substrate support adjacent the downstream side of the diffuser plate column.

In another embodiment, a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side; and a plurality of gas channels passing through the diffuser plate between the upstream side and the downstream side and between The downstream side includes a hollow cathode cavity, wherein the density of the hollow cathode cavity gradually increases from the center of the diffuser plate to the edge; and a substrate support column adjacent to the downstream side of the diffuser plate.

In another embodiment, a gas distribution plate assembly for a plasma processing chamber includes a diffuser plate having an upstream side and a downstream side, and the gas diffuser plate is divided into a plurality of coaxial regions and a plurality of The gas channels between the upstream side and the downstream side of the diffuser plate, wherein the gas channel in each zone is the same, and the density, volume and surface area of the hollow cathode cavity of the gas channel in each zone are obtained from the diffuser plate gradually increases from the center to the edge.

In another embodiment, a method of fabricating a gas distribution plate assembly for a plasma processing chamber includes fabricating a gas diffuser plate having an upstream side and a downstream side, and passing through the diffuser plate upstream and downstream Gas passages between the sides, bending the diffuser plate so that it is smooth convex towards the downstream side, and precision manufacturing the convex surface to flatten the downstream side surface.

In another embodiment, a method of manufacturing a gas distribution plate assembly for a plasma processing chamber includes precision fabricating a gas diffuser plate having an upstream side and a downstream side, and passing through the diffuser plate upstream side and a plurality of gas passages between the downstream side, wherein the density, volume and surface area of the hollow cathode cavity of the diffuser plate gradually increase from the center to the edge of the diffuser plate.

In another embodiment, a method of depositing a thin film layer on a substrate includes placing a substrate in a process chamber having a gas distribution plate having an upstream side and a downstream side for gas a diffuser plate, and a plurality of gas passages passing through the diffuser plate between upstream and downstream sides and comprising hollow cathode cavities on the downstream side, wherein either the bulk density of the hollow cathode cavities of the internal gas passages, or the The surface area density of the hollow cathode cavity, or the density of the hollow cathode cavity, is lower than the bulk density, surface area density, or density of the hollow cathode cavity of the external gas passage; allowing process gas to flow through a diffuser plate toward a support on a A substrate on a substrate support column, a plasma is created between the diffuser plate and the substrate support column, and a thin film layer is deposited on the substrate in the process chamber.

In another embodiment, a diffuser plate includes a body having a top surface and a bottom surface, a plurality of gas passages passing between the top and bottom surfaces, and an outer region and an inner region, wherein the The body between the top and bottom surfaces of the outer region is thicker than the body between the top and bottom surfaces of the inner region.

In another embodiment, a method of manufacturing a gas diffuser plate for a plasma processing chamber includes fabricating a gas diffuser plate having an upstream side and a downstream side, and passing through the diffuser plate upstream and downstream Multiple gas passages between the sides, and precision fabrication of the downstream surface to create the raised downstream surface.

In another embodiment, a method of making a gas distribution plate assembly for a plasma processing chamber includes bending a diffuser plate having an upstream side and a downstream side such that the downstream surface is concave and the upstream surface bulges, and creates a plurality of gas passages through the diffuser plate between the upstream and downstream sides by making the hollow cathode cavities nearly the same depth from an almost flat downstream surface To achieve, and make all the gas channels have the same size of open holes, these open holes are connected to each other to form the hollow cathode cavity.

Description of drawings

To help understanding, the same components in the illustrations are represented by the same component symbols;

1 is a schematic cross-sectional view of a bottom gate thin film transistor;

2 is a schematic cross-sectional view of a process chamber with a gas dispersion plate assembly of the present invention;

Fig. 3 is a schematic cross-sectional view of a gas dispersion plate;

4A is a flowchart of depositing a thin film layer on a substrate in a process chamber with a diffuser plate;

Figure 4B shows the measured deposition rate when a diffusion plate with uniform diffusion hole diameter and depth is deposited on a substrate of 1500 mm x 1800 mm;

Figure 5 shows both sides (501 and 502) of the substrate adjacent to the closed gas-filled channel and 5 measurement locations on the substrate;

Figure 6A (previous art) shows the concept of the hollow cathode effect;

Figures 6B-6G show various hollow cathode cavity designs;

Figure 7A shows the definition of "diameter (D)", "depth (d)" and "expansion angle ()" of a borehole extending to the downstream end of a gas channel;

Figure 7B shows the dimensions of a gas channel;

Figure 7C shows the dimensions of a gas channel;

Figure 7D shows the dimensions of a gas channel.

Figure 7E shows the distribution of gas channels on a diffuser plate;

Figure 8 shows the deposition rate measured on a 1500 mm x 1800 mm substrate with a diffusion plate having the gas channel distribution shown in Figure 7E;

Figure 9A shows a flow chart of making a diffuser plate;

Figure 9B shows a curved diffuser plate;

Figure 9C shows a diffuser plate that has been bent and its side facing the downstream side of the diffuser plate has been ground;

Figure 9D shows the depth profile of a diffuser plate with diffuser holes extending to the downstream end of the gas channel for processing a 1500 mm x 1850 mm substrate;

Figure 9E shows the deposition rate measured on a 1500 mm x 1850 mm substrate;

FIG. 9F shows the depth profile of a diffuser plate with diffuser holes extending to the downstream end of the gas channel for processing a 1870mm x 2200mm substrate;

Figure 9G shows the deposition rate measured on a 1870 mm x 2200 mm substrate;

FIG. 10A shows a flow chart of bending a diffuser plate with a heat treatment;

FIG. 10B a diffuser plate supported on a support frame in a heated environment used to bend the diffuser plate;

Figure 10C shows a curved diffuser plate on a support frame in a heated environment;

FIG. 11A is a flow chart of bending a diffuser plate with a vacuum process;

Figure 11B shows a diffuser plate on a vacuum module;

Figure 11C shows a curved diffuser plate on a vacuum module;

Figure 12A shows a flow chart for creating boreholes of different diameters and depths that can extend to the downstream side of the diffuser plate;

Figure 12B shows a cross-sectional view of the diffuser plate with boreholes of various diameters and depths that can extend to the downstream side of the diffuser plate;

Figure 12C - a diffuser plate with almost identical diffuser holes from the center to the edge;

Fig. 12D shows the bottom surface of the diffuser plate of Fig. 12C after it has been ground into a convex surface;

Fig. 12E shows the bottom surface of the diffuser plate in Fig. 12D after being pulled almost flat;

FIG. 12F shows a diffuser plate without any diffuser holes bent into a convex surface (bottom surface);

Figure 12G shows what the diffuser plate of Figure 12F would look like with diffusion holes;

Fig. 12H shows the bottom surface of the diffuser plate in Fig. 12G after being pulled almost flat;

Figure 12I shows what a diffusion plate with diffusion holes in multiple areas looks like;

Figure 12J shows a diffuser plate with mixed hollow cathode cavity diameters whose inner region hollow cathode cavity volume and/or surface area density is higher than its outer region hollow cathode cavity volume and/or surface area density;

Figure 12K shows a diffuser plate with mostly small hollow cathode cavities and only a few large hollow cathode cavities at the edges;

Figure 13 shows a schematic view of the downstream side of a diffuser plate with different diffuser hole densities.

Detailed ways

The above features of the present invention can be understood through the following detailed description of the invention and with reference to the embodiments and drawings. It should be noted that the accompanying diagram is only used to illustrate a specific embodiment of the present invention, and is not intended to limit the scope of the present invention, and the present invention also includes other equivalent changes of the embodiment.

The present invention provides a gas dispersion assembly for providing gas delivery in a process chamber. The invention described below will be described with reference to a plasma-enhanced chemical vapor deposition chamber designed to process large substrates, such as the plasma-enhanced chemical vapor deposition (PECVD) system manufactured and marketed by AKT, a division of Applied Materials, Inc. . However, it should be understood that the present invention can also be used in processes such as etching systems, other chemical vapor deposition systems, and any system that requires gas distribution in a process chamber, including those used to process circular substrates.

FIG. 1 shows a cross-section of a TFT structure. One of the common TFT structures is a back channel etch (back channel etch, BCE) inversion stack (or bottom gate) TFT structure as shown in FIG. 1 . It is preferred to use a BCE process because the gate dielectric (SiN) and the ingrown n+ doped amorphous silicon layer can be deposited in the same PECVD process. The BCE process shown here uses only five patterned masks. The substrate 101 may comprise a material that is almost completely transparent in the visible spectrum, such as glass or transparent plastic. The substrate can also be of any shape and size. Typically, for TFT applications, the substrate is a glass substrate with a surface area in excess of 500 mm2. A gate electrode layer 102 is formed on the substrate 101 . The gate electrode layer 102 includes a conductive layer that can control the movement of charged carriers in the TFT. The gate electrode layer 102 may also include a metal such as aluminum, tungsten, chromium, tantalum, or combinations thereof. The gate electrode layer 102 can be formed by conventional deposition techniques, lithography and etching techniques. Between the substrate 101 and the gate electrode layer 102, a selectively deposited insulating layer, such as a silicon dioxide layer or a silicon nitride layer, may be included, which may also be deposited by the PECVD system described herein. Afterwards, the gate electrode layer 102 is lithographically patterned and etched using known techniques to define the gate electrode.

A gate dielectric layer 103 is formed on the gate electrode layer 102 . The gate dielectric layer 103 may be a silicon dioxide layer, silicon oxynitride (SiON), or silicon nitride (SiN) layer, deposited by one embodiment of the PECVD system. The gate dielectric layer 103 is deposited with a thickness ranging from 100 angstroms to 6,000 angstroms.

A semiconductor bulk layer 104 is deposited on the gate dielectric layer 103 . The semiconductor bulk layer 104 may comprise polysilicon or amorphous silicon (-Si), which may be deposited by an embodiment of this PECVD system or other known methods. The semiconductor bulk layer 104 is deposited to a thickness ranging from 100 angstroms to 3,000 angstroms. A doped semiconductor layer 105 is deposited over the bulk semiconductor layer 104 . The doped semiconductor layer 105 may comprise n+ type (n+) or p-type (p+) doped polysilicon or amorphous silicon (-Si), which may be an embodiment of the PECVD system described above or other conventional method for deposition. The doped semiconductor layer 105 is deposited with a thickness ranging from 100 angstroms to 3,000 angstroms. One example of the doped semiconductor layer 105 is an n+ type doped -Si layer. Afterwards, the semiconductor bulk layer 104 and the doped semiconductor layer 105 are lithographically patterned and etched using known techniques to define the two layers overlying the gate dielectric insulating layer, which At the same time, it can also be used as a storage capacitor dielectric layer. The doped semiconductor layer 105 directly contacts a portion of the bulk semiconductor layer 104 to form a semiconductor junction.

Thereafter, a conductive layer 106 is deposited on the exposed surface. The conductive layer 106 includes a metal such as aluminum, tungsten, molybdenum (Mo), chromium, tantalum, or combinations thereof. The conductive layer 106 can be formed by known deposition techniques. Both the conductive layer 106 and the doped semiconductor layer 105 can be patterned to define source and drain regions in the TFT. Afterwards, a passive layer 107 may be deposited. A passive layer 107 conformally covers the exposed surface. The passive layer 107 is generally an insulating layer and may comprise, for example, a silicon dioxide layer or a silicon nitride (SiN) layer, and may be deposited by an embodiment of the PECVD system described herein or by other known methods. . The deposition thickness of the passive layer 107 ranges from 1000 angstroms to 5,000 angstroms. The passive layer 107 is then lithographically patterned by conventional etching techniques to open some contact holes in the passive layer 107 .

Thereafter, a transparent conductive layer 108 is deposited and patterned to be in contact with the conductive layer 106 . The transparent conductive layer 108 comprises a material that is substantially optically transparent and conductive in the visible spectrum. The transparent conductive layer 108 may include, for example, indium tin oxide (ITO) or zinc oxide. The transparent conductive layer 108 is patterned according to known etching techniques.

The doped or un-doped (endogenous) amorphous silicon (-Si), silicon dioxide for liquid crystal displays (or flat panel displays) can be deposited with one embodiment of the PECVD system described in the present invention (SiO ₂ ), silicon oxynitride (SiON) and silicon nitride (SiN) film layers. The TFT structure described is for illustration only, and the method of the present invention can be used in the fabrication of any device to which the present invention can be applied.

FIG. 2 shows an example of a plasma enhanced chemical vapor deposition system 200 manufactured and sold by AKT, a division of Applied Materials, Inc. (Santa Clara, California). The system 200 generally includes a process chamber 202 coupled to a gas source 204 . The process chamber 202 has walls 206 and a bottom 208 defining a portion of a process volume 212 . The process volume 212 is typically utilized through a port (not shown) located on the walls 206 to facilitate moving a substrate 240 into or out of the process chamber 202 . The plurality of walls 206 can support a cover assembly 210 that includes a plenum 214 for coupling the process volume 212 to an exhaust port (which includes various evacuation components, not shown).

A substrate support assembly 238 is positioned centrally in the process chamber 202 . The support assembly 238 can support a glass substrate 240 during processing. In one embodiment, the substrate support assembly 238 includes an aluminum body 224 in which at least one embedded heater 232 is sealed. The heater 232, such as a resistive element, located in the substrate support assembly 238 is coupled to an optional power source 274 and controllably heats the substrate support assembly 238 and the glass substrate 240 on the assembly 238 to a predetermined temperature. Typically, during a CVD process, the heater 232 maintains the glass substrate 240 at a uniform temperature between 150° C. and 460° C., depending on the process parameters of the deposited material.

In general, the substrate support assembly 238 has a lower side 226 and an upper side 234 . The upper side 234 can support the glass substrate 240 . The lower side 226 has a post 242 coupled thereto. The column 242 can couple the substrate support assembly 238 to a lift system (not shown) that moves the substrate support assembly 238 between a raised processing position (as shown) and a lowered position to facilitate Substrates are removed from or introduced into the process chamber 202 . The post 242 may also provide the passage of electrical and thermocouple leads between the substrate support assembly 238 and other components of the system 200 .

A bellows 246 is coupled between the substrate support assembly 238 (or the column 242 ) and the bottom 208 of the process chamber 202 . The bellows 246 can provide a vacuum seal between the process volume 212 and the atmospheric pressure outside the process chamber 202 while facilitating the vertical movement of the substrate support assembly 238 .

The substrate support assembly 238 is generally grounded so that RF power supplied by a power supply 222 to a gas distribution plate assembly 218 (or other electrodes within or near the chamber lid assembly) can be Gases are excited in process volume 212, wherein the gas distribution plate assembly 218 is between the lid assembly 210 and the substrate support assembly 238, and the process volume 212 is between the substrate support assembly 238 and the gas distribution plate Between components 218. The RF power from the power supply 222 is generally selected depending on the size of the substrate to drive the chemical vapor deposition process.

The substrate support assembly 238 may also support a shadow frame 248 . In general, the shadow frame 248 prevents deposition on the edge of the glass substrate 240 and the support member 238 so that the substrate does not stick to the support member 238 . The support assembly 238 has a plurality of holes 228 for receiving a plurality of lift pins 250 therein. The lift pin 250 is typically made of ceramic or anodized aluminum. The lift pin 250 is actuatable relative to the support assembly 238 by an optional lift plate 254 to protrude from the support surface 230 to place a substrate spaced from the support assembly 238 .

The lid assembly 210 provides an upper boundary of the process volume 212 . The lid assembly 210 typically can be removed or opened to service the process chamber 202 . In one embodiment, the cover assembly 210 is made of aluminum. The cover assembly 210 includes a plenum space 214 formed therein that is coupled to an external air extraction system (not shown). The plenum space 214 is used to uniformly discharge air and process by-products from the process space 212 out of the process chamber 202 .

The lid assembly 210 typically includes an inlet port 280 through which process gas provided by the gas source 204 is introduced into the process chamber 202 . The inlet port is also coupled to a clean gas source 282 . The cleaning gas source 282 may provide a cleaning agent (eg, dissociated fluorine) into the process chamber 202 to remove deposition by-products on the process chamber hardware, including the gas distribution plate assembly 218 .

The gas distribution plate assembly 218 is coupled to an inner side 220 of the cover assembly 210 . The gas distribution plate assembly 218 is typically configured to substantially track the shape of the glass substrate 240, such as a polygon for large area flat substrates and a circle for wafers. The gas distribution plate assembly 218 includes a perforated area 216 through which process and other gases provided by the gas source 204 are delivered into the process space 212 . The aperture area 216 of the gas distribution plate assembly 218 is configured to provide a uniform distribution of gas through the gas distribution plate assembly 218 and into the process chamber 202 . The gas distribution plate assembly can also be designed to have many of the advantages of the gas distribution plate assembly as disclosed in the following patent documents assigned to the applicant in the present case, including the U.S. patent application filed on August 8, 2001 by Keller et al. Patent Application No. 09/922,219; U.S. Patent Application No. 10/140,324, filed May 6, 2002 by Yim et al; U.S. Patent Application No. 1, filed January 7, 2003 by Blonigan et al 10/337,483; U.S. Patent No. 6,477,980, issued November 12, 2002 to White et al; U.S. Patent Application No. 10/417,592, filed April 16, 2003 by Choi et al; April 2004 US Patent Application No. 10/823,347 filed on the 12th by Choi et al; the entire disclosure of which is incorporated herein by reference.

The gas distribution plate assembly 218 typically includes a diffuser plate (or diffuser plate) 258 suspended from a suspension plate 260 . The diffuser plate 258 and the suspension plate 260 can also be made from a single piece. A plurality of gas channels 262 are formed through the diffuser plate 258 to allow a predetermined dispersed volume of gas to pass through the gas distribution plate assembly 218 and into the process volume 212 . The suspension plate 260 maintains the diffuser plate 258 and the inner surface 220 of the cover assembly 210 in a spaced apart state, so as to define an air-filled space 264 therebetween. The plenum space 264 allows gas to flow through the cover assembly 210 to be evenly distributed across the full width of the diffuser plate 258 so that the gas can be provided evenly over the central aperture area 216 and pass through it at an evenly distributed flow rate. Gas channel 262 .

The diffuser plate 258 is typically made of stainless steel, aluminum, anodized aluminum, nickel or other conductive material. The diffuser plate 258 can be cast, hammered, forged, hot pressed or calcined. The thickness of the diffuser plate 258 is such that sufficient flatness can be maintained on the hole 266 so as not to affect the processing operation of the substrate. The thickness of the diffuser 258 is between 0.8 inches and 2.0 inches. When manufacturing semiconductor wafers, the diffuser 258 can be circular, and when manufacturing flat panel displays, the diffuser 258 can be polygonal, such as rectangular.

FIG. 3 is a partial schematic view of an exemplary diffuser plate 258 as disclosed in U.S. Patent Application Serial No. 10/417,592, filed April 16, 2003, entitled " Gas Distribution Plate Assembly for Large Area Plasma Enhanced chemical Vapor Deposition". The diffuser plate includes a first or upstream side 302 facing the cap assembly 210 and an opposite second or downstream side 304 facing the support assembly 238 . Each gas channel 262 defined by a first bore 310 is coupled to a second bore 312 via an orifice hole 314 and merged to form a fluid flow through the diffuser plate 258 aisle. The first bore 310 extends from the upstream side 302 of the diffuser plate 258 to a first depth 330 to a bottom 318 . The bottom 318 of the first borehole 310 can be pointed (tapered), beveled (beveled), beveled (chamfered) or rounded to reduce the impact on the fluid when the fluid flows into the opening hole 314 from the first borehole. Fluid restrictions. The diameter of the first borehole 310 is typically 0.093 inches to 0.218 inches, and in one embodiment is 0.156 inches.

The second bore 312 is formed in the diffuser plate 258 and extends from the downstream side (or end) 304 to a depth 332 of 0.10 inches to 2.0 inches. Preferably, the depth 332 is between 0.1 inch and 1.0 inch. The diameter 336 of the second borehole 312 is generally between 0.1 inch and 1.0 inch, and can be expanded at an angle 316 of 10 degrees to 50 degrees. The diameter 336 is preferably between 0.1 inch and 0.5 inch, and the deployment angle 316 is between 20 degrees and 40 degrees. The surface area of the second borehole 312 is between 0.05 square inches and 10 square inches, and preferably between 0.05 square inches and 5 square inches. The diameter of the second borehole 312 refers to the diameter intersecting the downstream side 304 . An example diffuser plate for processing 150 mm x 1850 mm substrates has a second bore 312 that is 0.25 inches in diameter and spreads out at an angle of 22 degrees. The distance 380 between the edges 382 of adjacent second boreholes 312 is between 0 inch and 0.6 inch, preferably between 0 inch and 0.4 inch. The diameter of the first borehole 310 is typically, but not limited to, at least equal to or smaller than the diameter of the second borehole 312 . The bottom 320 of the second borehole 312 may be tapered, beveled, chamfered, or rounded to reduce the flow of gas when it exits the open hole 314 and enters the second borehole. Loss of pressure at 312 hours. In addition, the close proximity of the open hole 314 to the downstream side 304 minimizes the exposed surface area of the second bore 312 and the downstream side facing the substrate and reduces the exposure of the diffuser plate 258 to fluorine during chamber cleaning. The area on the downstream side of the system is used to reduce the probability of fluorine pollution in the deposited layer.

The open hole 314 generally couples the bottom 308 of the first borehole 310 and the bottom 320 of the second borehole 312 . The open hole 314 generally has a diameter between 0.01 inch and 0.3 inch, preferably between 0.01 inch and 0.1 inch, and typically has a length 334 between 0.02 inch and 1.0 inch, preferably between 0.02 inch and 0.5 inch. The length 334 and the diameter (or other geometry) of the open hole 314 are the main source of back pressure in the plenum space 264 that promotes an even distribution of gas across the upstream side 302 of the diffuser plate 258 . The open hole 314 is typically designed to be uniform across the plurality of gas passages 262; but the restriction from the open hole 314 can be designed to be uneven across the plurality of gas passages 262 to facilitate more gas flow through One area of the gas distribution plate 258, but not another area. For example, the open holes 314 can have a larger diameter and/or a shorter length 334 in the gas passages 262, or the gas distribution plate 258 is close to the walls 206 of the processing chamber 202, This allows more gas to flow through the edges of the apertured region 216 to increase the deposition rate around the perimeter of the glass substrate. The thickness of the diffuser is between 0.8 inches and 3.0 inches, preferably between 0.8 inches and 2.0 inches.

As the substrate size continues to increase in the TFT-LCD industry, especially when the substrate is at least 1000 mm x 1200 mm (or 1,200,000 mm2), the film thickness and property uniformity of large-area plasma-enhanced chemical vapor deposition (PECVD) also become increasingly important. Uniformity issues include higher deposition rates and tighter film layers in the central region of large substrates for certain high-speed deposited silicon nitride layers. The uniformity of the film on the substrate appeared to be thicker and "domeshaped" in the central region than in the peripheral regions. Layers that are less constricted in the edge region have a higher Si-H content. TFT-LCD fabrication conditions include low Si-H content (e.g., <15 atomic %), high deposition rate (e.g., >1500 Angstroms/min), and low thickness non-uniformity (e.g., <15% ). The Si—H content is calculated from FTIR (Fourier Transform Infrared) measurements. Large substrates have the worst "dome" uniformity problems. This problem cannot be eliminated by changing the process recipe to satisfy all conditions. Therefore, it is necessary to solve the problem by improving the gas and/or plasma distribution.

The process of depositing a thin film layer in the process chamber is shown in Figure 4A. The process begins at step 401 by placing the substrate into a process chamber with a diffuser plate. Next, in step 402, process gas is flowed through a diffuser plate toward a substrate supported on a substrate support. Then in step 403, a plasma is created between the diffuser plate and the substrate support. In step 404, a thin film layer is deposited on the substrate in the processing chamber. FIG. 4B shows a typical thickness profile of a silicon nitride film on a glass substrate. The substrate area is 1500 mm x 1800 mm. The diffusion plate has diffusion holes as shown in FIG. 3 . The diameter of the first bore 310 is 0.156 inches. The length 330 of the first bore 310 is 1.049 inches. The second bore 312 has a diameter 336 of 0.250 inches. The spread angle 316 of the second borehole 312 is 22 degrees. The second bore 312 has a length 332 of 0.243 inches. The open hole 314 has a diameter of 0.016 inches and a length of 0.46 inches. The silicon nitride layer was deposited with 2800 sccm of _SiH4 , 9600 sccm of _NH3 and 28000 sccm of _N2 under 1.5 Torr pressure and 15000 watts of power. The distance between the diffuser plate and the substrate support assembly was 1.05 inches. The process temperature is maintained at 355°C. The average deposition rate was 2444 Å/min and the film thickness uniformity (15 mm edge exclusion rate) was 25.1%, which was much higher than the process specification (<15%). The thickness pattern shows a central thicker pattern or "dome-like" pattern. Table 1 shows the film properties measured from wafers placed on the glass substrate.

Table 1 measures the film thickness and properties of substrates with silicon nitride deposition layers

Edge I and Edge II respectively represent the two ends of the substrate with a width of 1800 mm. The reflectance (RI), film stress, SiH concentration data, and wet etch rate (WER) data show that the film near the center of the substrate is more compressed than the film at the edge of the substrate. The SiH concentration at the edge of the substrate is close to 15% of the process boundary condition. The wet etch rate was measured by immersing the sample in a 6:1 solution of BOE (buffered oxide etch).

One of the theories that can be used to explain the unevenness of the center than the edge is that there is an excessive amount of residual gas between the diffuser plate and the substrate and the central area of the substrate that cannot be effectively removed, resulting in a higher deposition rate and tighter in the central area of the substrate. film layer. Sample tests are designed to see if the theory is correct. As shown in FIG. 5 , in a PECVD process chamber, a heat-resistant adhesive tape is used to block the pumping channels 214 near the substrate 501 and 502 sides (shown in FIG. 2 ). The suction channels 214 close to the other two sides are opened so that they can pass freely. Thus, an asymmetric gas pumping state is created. If the cause of the "domed" problem is the inability to pump away excess residual gas from the edge of the substrate, the non-uniformity problem at the edge of the substrate with heat-resistant tape will be exacerbated, and the non-uniformity problem across the substrate will be more serious. deterioration. However, comparing the deposition results when the two pumping channels are blocked with the deposition results when all the pumping channels are open, there is not much difference in the deposition results (see Table 2). The design and dimensions of the diffuser plate used here are the same as those used in FIG. 4B and Table 1. The silicon nitride layer in Table 2 was deposited with 3300 sccm of SiH ₄ , 28,000 sccm of NH ₃ and 18,000 sccm of N ₂ at a pressure of 1.3 Torr and a power of 11,000 watts. The distance between the diffuser plate and the substrate support assembly was 0.6 inches. The process temperature is maintained at 355°C. The film thickness and its properties were measured at positions 1, 2, 3, 4 and 5 (as shown in Figure 5) respectively. The SiH contents shown in Table 2 are atomic %.

Table 2 compares the film thickness and properties of the silicon nitride deposition layer when all the pumping channels are opened and when two pumping channels are blocked

The results in Table 2 show that there is no significant difference in the film thickness and properties of the silicon nitride deposition layer when all the pumping channels are opened and when the two pumping channels are blocked. Also, there was minimal difference in the results collected at measurement locations 1 and 5, which would have been the case if residual gas was the cause of the problem. Therefore, the theory that there is an excess of residual gas between the diffuser plate and the substrate and in the central area of the substrate that cannot be effectively removed, resulting in a higher deposition rate and a tighter film layer in the central area of the substrate is not correct.

Another possible cause of non-uniform deposition in the central region versus the edges is plasma non-uniformity. Deposition of films by PECVD is almost entirely dependent on plasma activation. A dense chemically reactive plasma can be generated due to the hollow cathode effect. The driving force for a hollow cathode discharge generated at RF is the frequency modulated DC potential Vs (self-bias potential) across the RF electrode space charge sheath. Figure 6A shows the oscillatory motion of electrons between an RF hollow cathode and a mutually repelling electric field (Es) of opposite charge sheaths. Electrons emitted from the cathode wall (which may be the wall of the reactive gas channel near the process volume) are accelerated by the electric field Es on the wall sheath "δ". Electrons between the electrode walls can vibrate across the interior space due to the mutually repelling electric fields on the opposite wall sheaths. The electrons lose energy by colliding with the gas and create more ions. The ions created can be accelerated to the cathode wall, thereby promoting the emission of secondary electrons to create more ions. Overall, the cavity between the cathode walls can enhance the emission of electrons and the dissociation of gases. The expanded trumpet-shaped cathode wall and the diameter of the gas inlet are smaller than the diameter of the gas outlet, which can more effectively release the gas than the cylindrical wall. At the same time, a potential difference Ez is also caused due to the difference in dissociation efficiency between the gas inlet and the gas outlet.

By changing the design and the arrangement (or density) of the hollow cathode wall cavities near the process space 212 (which is facing the substrate and located at the downstream end of the holes (or channels) of the gas diffusion plate), the gas density can be changed. The degree of freeness is used to control the thickness and property uniformity of the film layer. An example of a wall of the hollow cathode cavity adjacent to the process volume 212 is the second bore 312 shown in FIG. 3 . The hollow cathode effect mainly occurs at the expanded horn impingement area 312 facing the process volume 212 . The design of Figure 3 is for illustration only. The invention is also applicable to other types of hollow cathode cavity designs. Other examples of hollow cathode cavity designs include, but are not limited to, the designs in Figures 6B-6G. By varying the volume and/or surface area of the hollow cathode cavity, the plasma ionization rate can be varied.

Taking the design of FIG. 3 as an example, the volume of the second borehole 312 (or hollow cathode chamber) can be changed by changing the diameter "D" (or diameter 336 in FIG. 3 ), depth "d" (or length in FIG. 3 332) and the deployment angle "" (or the deployment angle 316 in Figure 3), as shown in Figure 7A. Changing the diameter, depth and angle of deployment will result in a change in the surface area of the borehole 312 . This is most likely due to the high plasma density due to the higher deposition rate and tighter film layers in the center of the substrate. By reducing the depth of the diffusion plate from the edge to the center, the diameter, the spread angle, or a combination of these factors, the plasma density in the central region of the substrate can be reduced to improve the film thickness and its uniformity. Reducing the borehole depth, diameter, and spread angle also reduces the surface area of the borehole 312 . Figures 7B, 7C and 7D show 3 designs of diffusion channels (or diffusion holes), which are arranged on the diffusion plate as shown in Figure 7E. The designs of Figures 7B, 7C and 7D have the same borehole diameter, but the borehole depth and total borehole surface area are the largest in the design of Figure 7B but the smallest in the design of Figure 7D. The spread angle of the borehole has been changed to match the final borehole diameter. Figure 7B is drilled to a depth of 0.7 inches. The drilling depth of Figure 7C was 0.5 inches and the drilling depth of Figure 7D was 0.325 inches. The smallest rectangle 710 in Figure 7E is 500 mm x 600 mm in size and the diffusion hole has a drilled depth of 0.325 inches, a drilled diameter of 0.302 inches, and a spread angle of 45 degrees (see Figure 7D). The size of the medium rectangle in Figure 7E is 1000 mm x 1200 mm. The diffusion holes in region 720 between the medium rectangular region and the smallest rectangular region have a drilled depth of 0.5 inches, a drilled diameter of 0.302 inches, and a spread angle of 30 degrees (see FIG. 7C ). The largest rectangle size in Figure 7E is 1500 mm x 1800 mm. The diffusion holes in region 730 between the largest rectangle and the medium rectangle region have a drilled depth of 0.7 inches, a drilled diameter of 0.302 inches, and a spread angle of 22 degrees (see FIG. 7B ). In FIGS. 7B , 7C and 7D , the diameters of the open holes are all 0.03 inches, and the hole depths are all 0.2 inches. All three diffusers are 1.44 inches thick. The diameter of the first borehole in Figures 7B, 7C and 7D is 0.156 inches and its depth is 0.54 inches (FIG. 7B), 0.74 inches (FIG. 7C) and 0.915 inches (FIG. 7C), respectively.

Figure 8 shows the deposition rate on the substrate. Region I represents the area at a drilling depth of 0.325 inches, and Regions II and III represent the area at depths of 0.5 inches (Region II) and 0.7 inches (Region III), respectively. Table 3 shows the measured film thickness and its uniformity on the substrate. The silicon nitride films in Table 3 were deposited with 3300 sccm SiH ₄ , 28000 sccm NH ₃ and 18000 sccm N ₂ at a pressure of 1.3 Torr and an electric power of 11000 watts. The distance between the diffuser plate and the substrate support assembly was 0.6 inches. The process temperature is maintained at 355°C. Positions 1, 2, 3, 4 and 5 are shown in Figure 5.

Table 3 compares the film thickness and properties of the silicon nitride deposition layer with 3 different depths of diffusion plates.

The results in Table 3 show that decreasing the borehole depth and the borehole surface area will reduce the deposition rate. In addition, the results in Table 3 also show that reducing the volume and/or surface area of the hollow cathode cavity also reduces the deposition rate. A decrease in plasma deposition rate represents a decrease in plasma ionization rate. The deposition rate on the substrate shown also exhibits 3 different regions due to non-uniform changes in drilling depth and total drilled surface area from region I to region II to region III. Regions I, II and III on the substrate correspond to the diffusion hole regions 710 , 720 and 730 . This indicates that changing the design of the hollow cathode cavity can change the plasma ionization rate, and the importance of smooth and gradual changes.

There are many ways to gradually change the hollow cathode cavity from the inner area of the diffuser plate to the outer area of the diffuser plate to improve plasma uniformity. One way is to first bend the diffuser plate (which has the same gas diffusion channels throughout the diffuser plate) to a predetermined curvature, and then smooth the curvature to flatten the surface. Figure 9A is a flowchart of this concept. The process begins at step 901 by bending the diffuser to a curvature, and then at step 902 smoothes the curved diffuser so that the surface of the diffuser is flat again. FIG. 9B shows a curved diffuser plate with exemplary diffuser holes 911 and 912 at the edge (and outer region) and center (and inner region), respectively. Before the bending step, the diffusion holes 911 and 912 are identical and are simply shown in Figures 3 and 7A. However, the present invention can be used in any diffusion hole design. The design of Figure 3 is merely an illustration. The downstream surface 304 of the diffuser plate faces the process volume 212 . There is a gradual change between the 913 surface and the imaginary surface 914 (shown in dotted lines since it does not exist) to show its curvature. Before bending, the size and shape of the edge diffusion hole 915 and the central diffusion hole 916 are the same. FIG. 9C is a schematic diagram of a diffuser plate after its curvature has been mechanically smoothed. The surface facing the process volume 212 has been ground to a flat surface 914 such that the central borehole 918 is significantly shorter than the edge boreholes 917 . Since the borehole size (volume and/or surface area) is changed by first bending and then grinding the diffuser plate, the change in volume from the center of the borehole to the edge is gradual. The central borehole 918 will be shorter in diameter "D" and depth "d" than the edge borehole 917. The definition of the diameter "D" and the depth "d" of the borehole can be referred to the text description of FIG. 7A.

Figure 9D shows the depth "d" of the bore 312 extending to the downstream side of an exemplary diffuser plate for processing 1500 mm x 1850 mm substrates. The diffusion plate has a design of diffusion holes as shown in Fig. 7A. The diameter of the first bore 310 is 0.156 inches. The length 330 of the first bore 310 is 1.049 inches. The second bore 312 has a diameter of 0.250 inches. The spread angle of the second borehole 312 is 22 degrees. The length 332 of the second bore 312 is 0.243 inches. The diameter of the open hole 314 is 0.016 inches and the length of the open hole 314 is 0.046 inches. The depth measurement of the second borehole in FIG. 9D shows that a borehole depth 332 (or "d" in FIG. 7A ) gradually increases from the center of the diffuser plate to the edge of the diffuser plate. Due to the bending and grinding process, the diameter 336 (or "D" in FIG. 7A ) of the diffuser plate 312 also gradually increases from the center of the diffuser plate to the edge of the diffuser plate.

FIG. 9E shows the thickness distribution of the deposited film layer on the substrate on which the silicon nitride film is deposited using the diffuser plate with the design shown in FIGS. 9B, 9C and 9D. The size of the substrates processed was 1500 mm x 1850 mm, which is only slightly larger than the substrates in Figure 4B and Table 1 (1500 mm x 1800 mm). In general, the size of the diffuser plate must be properly adjusted as the size of the substrate being processed changes. The size of the diffuser used to handle the 1500mm x 1850mm substrate is 1530mm x 1860mm, which is slightly larger than the 1500mm x 1800mm substrate (its diffuser is 1530mm x 1829mm). The thickness uniformity improved by 5.0%, which is much lower than the 25.1% ratio in Figure 4B. Table 4 shows the distribution of film properties on the substrate. The diffusion plate has a design of diffusion holes as shown in Fig. 7A. The diameter of the first bore 310 is 0.156 inches. The length 330 of the first bore 310 is 1.049 inches. The second bore 312 has a diameter of 0.250 inches. The spread angle of the second borehole 312 is 22 degrees. The length 332 of the second bore 312 is 0.243 inches. The diameter of the open hole 314 is 0.016 inches and the length of the open hole 314 is 0.046 inches. The silicon nitride film in FIG. 9E and Table 4 was deposited with 2800 sccm of SiH ₄ , 9600 sccm of NH ₃ and 28000 sccm of N ₂ at a pressure of 1.5 Torr and an electric power of 15,000 watts. The distance between the diffuser plate and the substrate support assembly was 1.05 inches. The process temperature is maintained at 355°C. Edge I and Edge II represent the two ends of the substrate, respectively, and are as described in Table 1. Compared to the data in Table 1, the film thickness and property data in Table 4 show a smaller center-to-edge variation.

Table 4 compares the thickness and properties of the deposited silicon nitride film layers on a 1500mm x 1850mm substrate treated with a diffuser plate having gradually varying drilling depths and diameters from the center to the edge

Comparing the data in Table 4 and Table 1, these data are collected during the deposition process with the diffusion plate having the same diameter and depth of the drilled hole 312 on the diffusion plate, it can be found that regardless of the thickness change, stress, Si-H Content and wet etching rate (WER), the data values in Table 1 are less than the values in Table 4. The data in Table 4 are deposited on a diffusion plate with a drill hole diameter and depth that gradually increases from the center of the diffusion plate to the edge data collected at the time. The results show that the thickness and uniformity of the film layer can be improved by gradually increasing the diameter and depth of the drilled holes from the center to the edge, and the drilled holes are extended downstream of the diffuser plate. The wet etch rates in the table are measured by soaking the samples in a 6:1 solution of BOE.

Figure 9F shows measurements of the depth "d" of drilled holes 312 on an exemplary diffuser plate for processing 1870 mm x 2200 mm substrates, curve 960 shows an ideal drilled hole depth distribution on the diffuser plate example. The measurement of the drilling depth in FIG. 9F shows that the drilling depth gradually increases from the center to the edge of the diffuser plate. The diameter of the downstream drilling hole also gradually increases from the center of the diffusion plate to the edge.

FIG. 9G shows the thickness distribution of a silicon nitride film layer deposited on a substrate treated with a diffuser plate having a design similar to that of FIGS. 9B, 9C and 9F. The substrate has a size of 1870 mm x 2200 mm. Table 5 shows the distribution of film properties on the substrate. The diffusion plate has a design of diffusion holes as shown in Fig. 7A. The diameter of the first bore 310 is 0.156 inches. The length 330 of the first bore 310 is 0.915 inches. The second bore 312 has a diameter of 0.302 inches. The spread angle 316 of the second borehole 312 is 22 degrees. The length 332 of the second bore 312 is 0.377 inches. The diameter of the open hole 314 is 0.018 inches and the length of the open hole 314 is 0.046 inches. The silicon nitride films in Table 5 were deposited with 5550 sccm of SiH ₄ , 24700 sccm of NH ₃ and 61700 sccm of N ₂ at a pressure of 1.5 Torr and an electric power of 19,000 watts. The distance between the diffuser plate and the substrate support assembly was 1.0 inches. The process temperature is maintained at 355°C. Edge I and Edge II represent the two ends of the substrate, respectively, and are as described in Table 1. Compared to the data in Table 1, the film thickness and property data in Table 5 show a smaller center-to-edge variation. The uniformity of the film layer is 9.9%, which is better than 25.1% in Fig. 4B. Compared with the substrate (1870 mm x 2200 mm) data in Figure 9G and Table 5, the data in Figure 4B and Table 1 are the film thickness and uniformity measured on a smaller substrate (1500 mm x 1800 mm). It is expected that the film thickness and uniformity will be worse for larger substrates. The 9.9% uniformity and improved film property data measured with the new design in Table 5 shows that the new design, that is, the diameter and depth of the drilled holes on the diffuser plate extending to the downstream side of the diffuser plate from the center of the diffuser plate to the edge Gradually increasing the plasma uniformity and process uniformity can be greatly improved.

Table 5 compares the thickness and properties of silicon nitride films deposited on substrates of 1870 mm x 2200 mm treated with diffuser plates having progressively varying drilling depths and diameters from center to edge

Although the diffuser plate shown is rectangular in shape, the invention is applicable to diffuser plates of other shapes and sizes. Note that the curvature of the downstream surface must be ground completely flat. As long as the diameter and depth of the drilled holes gradually increase from the center of the diffuser plate to the edge, the edge of the diffuser plate does not need to be ground.

There are also many ways to create curvature in this diffuser. One way is to support the edges of the diffuser plate with supports and heat treat the diffuser plate for a period of time at a temperature sufficient to soften the diffuser plate (eg, a temperature greater than 400° C. for aluminum). When the metal diffuser is softened under high temperature treatment, gravity will cause the center of the diffuser to hang down and make the diffuser bend. Figure 10A shows a process flow diagram 1000 for such a heat treatment. Firstly, in step 1001, place the diffuser plate with the diffusion holes therein in the environment 1005 or a temperature-controlled process chamber, and place the diffuser plate 1010 on the supporter 1020 that can only support the edge of the diffuser plate ( See Figure 10B). The diffuser plate facing downward is the downstream side 304 of the diffuser plate. After step 1002, the ambient temperature is raised and the diffuser plate is treated at a temperature that softens the diffuser plate. One embodiment is to maintain the heated environment at the constant temperature once the constant temperature is reached. When the curvature of the diffusion plate reaches the desired curvature, the heat treatment step is stopped (step 1003 ). It should be noted that in a heated environment, an optional diffuser plate supporter 1030 can be placed under the diffuser plate 1010 at a support height 1035 lower than the support height 1025 of the supporter 1020 and a support distance 1027 than the supporter 1020 Also a short support distance of 1037. The optional diffuser plate supporter 1030 can help determine the curvature of the diffuser and can be made of elastic material that can withstand high temperature above 400°C (the same temperature as the heat treatment environment) without damaging the surface of the diffuser plate. FIG. 10C shows the heat-treated curved diffuser plate 1010 placed on the diffuser plate holders 1020 and 1030 .

Another way to create curvature is to use a vacuum to smoothly bend the diffuser plate into a convex shape. FIG. 11A shows a flow 1100 of such vacuum processing. First, in step 1101 , the diffuser plate having diffuser holes therein with the downstream side 304 facing downward is placed on a vacuum assembly 1105 and the upstream end 302 of the diffuser plate is sealed with a cover. The mechanical strength of the material used to cap (or seal) the upstream end of the diffuser plate must be sufficient to maintain its integrity under vacuum. The vacuum assembly only supports the substrate at the edge of the substrate with diffuser plate holders 1120 (see FIG. 11B ). The vacuum assembly 1105 is designed with a vacuum channel 1150 to evacuate the volume 1115 between the diffuser plate and the vacuum assembly 1105 when the upstream end of the diffuser plate is covered. The vacuum channels 1150 in Figures 11B and 11C are only used to illustrate this concept. There may be more than one vacuum channel 1150 , located at various locations in the vacuum assembly 1105 . Then at step 1102, the volume 1115 between the diffuser plate and the diffuser plate holder is evacuated. When the curvature of the diffuser plate reaches the desired curvature, the step of vacuuming is stopped at step 1103 and the pressure of the volume 1115 between the diffuser plate and the vacuum assembly is restored to be the same as that of the surrounding environment 1140 to The diffusion plate is allowed to be removed from the vacuum assembly 1105 . It should be noted that in the vacuum assembly, an additional diffuser plate supporter 1120 can be placed below the diffuser plate 1110 at a lower support height 1135 than the support height 1125 of the diffuser plate supporter 1120 and at a lower support height than the supporter 1120 The support distance 1137 is shorter than the support distance 1127 . The additional diffuser support 1120 can help terminate the curvature of the diffuser and can be made of a material such as rubber that will not damage the surface of the diffuser. 11C shows the curved diffuser plate 1110 placed on the diffuser plate supporters 1120 and 1130 after bending.

Another way to vary the depth of the downstream cone (312 in FIG. 3 ), the diameter of the cone, the angle of expansion of the cone, or a combination of the three parameters is to drill the diffuser holes at different angles from the center of the diffuser plate to the edges. Conical Depth, Conical Diameter, Conical Expansion Angle for . The drilling action can be achieved by computer numerical control (CNC) grinding. Figure 12A shows a process flow diagram for such a process 1200. The process 1200 begins at step 1230 by creating boreholes that extend to the downstream side of the diffuser plate with increasing depth and/or diameter from the center of the diffuser plate to the edges. The deployment angle can also be gradually changed from the center of the diffusion plate to the edge. Next at step 1240, the remainder of the diffuser plate gas channels are created. A drilling tool may be used to create downstream boreholes. If a drilling tool with the same spread angle is used across the diffuser plate, the spread angle of the drilled holes will remain constant while the drilled hole depth and diameter can be varied. The diameter of the borehole can be determined by the spread angle and the depth of the borehole. It is important to vary the drilling depth smoothly and gradually to ensure smooth deposition thickness and film uniformity across the substrate. Figure 12B shows an example with different drilling depths and diameters. The diffusion hole 1201 is near the center of the diffusion plate and has the smallest drilling depth 1211 and drilling diameter 1221 . The diffusion hole 1202 is located between the center and the edge of the diffusion plate and has a medium drilling depth 1212 and a medium drilling diameter 1222 . The diffusion hole 1203 is near the edge of the diffusion plate and has a maximum drilling depth 1213 and a maximum drilling diameter 1223 . The conical spread angles are the same for all diffusion holes in the design of Figure 12B. However, it is also possible to optimize the deposition uniformity by changing the design of the holes on the diffuser plate by varying the depth, diameter and spread angle of the holes. Changing the depth, diameter and spread angle of the borehole will affect the surface area of the overall borehole and also affect the hollow cathode effect. A smaller borehole surface area reduces the ionization efficiency of the plasma.

Another way to vary the depth (d), diameter (D) of the downstream boreholes (312 in Figure 3) is by drilling the same diffuser holes throughout the diffuser plate (see Figure 12C). In FIG. 12C , the gas diffusion holes 1251 at the edge (an outer region) of the diffuser plate are the same as the gas diffusion holes 1252 at the center (an inner region) of the diffuser plate. The downstream bore 1255 is the same as the downstream bore 1256 . The downstream surface 1254 of the gas diffuser plate is initially flat. Then, the downstream side of the diffuser plate is ground to make a concave surface so that the center is thinner than the edge. The milling can be accomplished by computer numerically controlled (CNC) milling or other controllable and repeatable milling types. After grinding the downstream surface 1254 to a concave surface (face 1259), the downstream bore 1258 in the center of the diffuser plate (inner region) has a smaller diameter (D) than the downstream bore 1257 at the edge of the diffuser plate (outer region). and shorter lengths (d). The diffuser plate can be left in this way as shown in FIG. 12D, or the downstream surface 1259 can be flattened as shown in FIG. 12E, or drawn into other curvatures (not shown) for use in a process chamber to achieve desired film layer results.

Another way to vary the depth (d), diameter (D) of the downstream bore (312 in Figure 3) is by bending the diffuser plate without the diffuser holes in it into a concave shape (see Figure 12F). In FIG. 12F , this downstream face is imaginary face 1269 . A downstream borehole of the same depth is then drilled from this imaginary face 1264 with a drilling tool (see FIG. 12G ). Although the downstream borehole in the center of the diffuser plate is drilled from the imaginary face 1264 to the same depth as the downstream borehole 1267, the diameter and length of the downstream borehole 1268 are smaller than the diameter and length of the downstream borehole 1267. The length comes small. The rest of the diffusion hole, including the opening hole 1265, the upstream bore 1263 and the connection bottom, is ground down to complete the diffusion hole. All open holes and upstream boreholes should be of the same diameter, although this is not required. It is also necessary to maintain the same diameter and length of the opening hole on the entire diffusion plate (as shown in FIG. 12G ). The open hole controls the back pressure. By keeping the diameter and length of the opening holes on the entire diffuser plate the same, the back pressure that will affect the airflow can also be kept constant on the entire diffuser plate. The diffuser plate can be kept in this way as shown in FIG. 12G, or the downstream surface 1269 can be flattened as shown in FIG. 12H, or drawn into other curvatures (not shown) for use in a process chamber to achieve desired film layer results.

The change in diameter and/or length of the hollow cathode cavity from the center to the edge of the diffuser plate does not need to be a perfect, continuous change as long as the change is smooth and gradual. It can also be achieved by arranging several uniform regions in a concentric pattern, as long as the change from one region to another is smooth and gradual. Overall, however, the size (volume and/or surface area) of the hollow cathode cavity must increase from the center of the diffuser plate towards the edges. Figure 12I shows a schematic view of the bottom of a diffuser plate (looking down from the downstream side). The diffuser plate is divided into N coaxial regions. The coaxial region is defined as the area between an inner and an outer boundary, which has the same geometry as the overall diffuser shape. From region 1 to region N, the size (volume and/or surface area) of the hollow cathode cavity increases stepwise. This increase can be achieved by increasing the diameter, length, flare angle, or a combination of these factors of the hollow cathode cavity.

Increasing the diameter and/or length of the hollow cathode cavities from the center to the edge of the diffuser plate need not be effective for all of the diffuser holes, as long as the overall size of the hollow cathode cavity per downstream diffuser plate surface area increases. For example, the size of some diffusion holes on the diffusion plate can be kept constant, while the size of the hollow cathode cavity of other diffusion holes can be gradually increased from the center to the edge of the diffusion plate. In another embodiment, the diffuser holes have hollow cathode cavities of increasing size (volume and/or surface area), while the edge of the diffuser plate has very small hollow cathode cavities, as shown in FIG. 12J . In another embodiment, the volume of most of the hollow cathode cavities on the diffuser plate is uniform, and only a small number of very large hollow cathode cavities are located at the edge of the diffuser plate, as shown in FIG. 12K .

We define the volume of the hollow cathode chamber as the volume of the central cathode chamber per the surface area of the downstream diffusion holes of the central cathode chamber. Similarly, the central cathode cavity surface area density of the central cathode cavity may also be defined as the central cathode cavity surface area per downstream diffusion hole surface area of the central cathode cavity. The above results show that plasma and process uniformity can be improved by gradually increasing the volume of the central cathode chamber or the surface area density of the central cathode chamber from an inner region to an outer region of the diffuser plate.

Another way to change the thickness of the film layer and the uniformity of properties is to change the density of diffusion holes on the diffusion plate, but keep the design of the diffusion holes themselves unchanged. The density of the diffuser holes can be calculated by dividing the total surface area of the holes 312 intersecting the downstream side 304 by the total surface area of the downstream side 304 of the diffuser plate in the measurement region. The density of diffusion holes can vary from 10% to 100%, and preferably from 30% to 100%. In order to reduce the "dome shaped" problem of the coating, the density of diffusion holes in the inner region needs to be lower than that in the outer region to reduce the plasma density in the inner region. The density change from the inner region to the outer region must be gradual and smooth to ensure that the deposited film layer has a uniform and smooth thickness and properties. Figure 13 shows a stepwise change in diffusion hole density from a low density in the center (region A) to a high density at the edge (region B). The low density of diffusion holes in the central region reduces the plasma density and "dome shaped" problems in the central region. The arrangement of diffusion holes in FIG. 13 is only used to show how to increase the density of diffusion holes from the center to the edge. Any arrangement and pattern of diffusion holes is applicable to the present invention. The concept of density variation can also be used in combination with the concept of changing the design of the diffusion holes to improve the uniformity from the center to the edge. When plasma uniformity is achieved by varying the density of the gas channels, the distance between the downstream end hollow cathode cavities can exceed 0.6 inches.

The concept of gradually increasing the size (volume and/or surface area) of the hollow cathode cavity from the center of the diffuser plate to the edge of the present invention can be used to bend the diffuser plate and any available hollow cathode cavity grinding method with or without changing the diffusion hole density. Either, by combining any of the size (volume and/or surface area) and shape variations of the hollow cathode cavity. For example, the concept of gradually increasing the density of diffusion holes from the center to the edge of the diffuser plate can be used to gradually increase the diameter of the hollow cathode cavity (or downstream drilling) from the center to the edge of the diffuser plate. The diffusion plate can be kept flat and the diffusion holes can be CNC drilled. There are many combinations available. Therefore, this concept can meet the requirements of film thickness and property uniformity.

So far, various embodiments of the present invention describe how to gradually increase the length and diameter of the hollow cathode cavity from the center to the edge of the diffuser plate, so as to improve the plasma uniformity on the substrate. However, in some cases, it is necessary to gradually reduce the length and diameter of the hollow cathode cavity from the center of the diffuser plate to the edge. For example, the power near the center of the substrate is too low, so larger hollow cathode cavities are required to compensate for this lower power. Therefore, the concept of the invention can also be used in cases where the size (volume and/or surface area) of the hollow cathode cavity is gradually reduced from the center to the edge of the diffuser plate.

The concept of the present invention can be applied to any design of gas diffusion holes, including any design of hollow cathode cavity, any design of gas diffusion plate shape/size. The inventive concept can be applied to any gas diffusion plate using a variety of gas diffusion hole designs. The concept of the present invention can also be applied to any curvature and made of any material (such as aluminum, tungsten, chromium, tantalum, or a combination thereof), any method (such as casting, tapping, forging, hot pressing or forging) diffuser plate. The inventive concept can also be applied to gas diffusion plates with layers pressed or bonded together. In addition, the present invention can also be applied in a process chamber of a cluster system, a stand-alone system, an in-line system, or any available system.

While the present invention has been particularly shown and described using embodiments of the present invention, it will be understood by those skilled in the art that other changes in form and details as described above may be made without departing from the scope of the present invention. And the spirit is achieved. Accordingly, the present invention is not limited to the exact forms and details shown and described, but falls within the scope defined by the following claims.

Claims (105)

1. A gas distribution plate assembly for a plasma process chamber, comprising at least: a diffuser plate element having an upstream side and a concave downstream side; and Inner and outer gas channels, which are located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, The conical or cylindrical second diameter or depth or the combination of the two gradually increases from the center of the diffuser plate element to the edge, and the hollow cathode cavity of the inner gas channel is smaller than the hollow cathode cavity of the outer gas channel cavity size. 2. The gas distribution plate assembly of claim 1, wherein the second diameter is between 0.1 inch and 1.0 inch. 3. The gas distribution plate assembly of claim 1, wherein the second diameter is between 0.1 inch and 0.5 inch. 4. The gas distribution plate assembly of claim 1, wherein the depth of the conical or cylindrical shape is between 0.1 inches and 2.0 inches. 5. The gas distribution plate assembly of claim 1, wherein the depth of the conical or cylindrical shape is between 0.1 inch and 1.0 inch. 6. The gas distribution plate assembly of claim 1, wherein the angle of expansion in the cone is between 10 degrees and 50 degrees. 7. The gas distribution plate assembly as claimed in claim 1, wherein the expansion angle of the conical shape is between 20 degrees and 40 degrees. 8. The gas distribution plate assembly of claim 1, wherein the second diameter is between 0.1 inch and 1.0 inch, the depth of the conical or cylindrical shape is between 0.1 inch and 2.0 inch, and The expansion angle of the conical shape is between 10° and 50°. 9. The gas distribution plate assembly of claim 1 wherein the spatial distance between the downstream ends of the hollow cathode cavities of adjacent gas passages is at most 0.6 inches. 10. The gas distribution plate assembly of claim 1, wherein the thickness of the diffuser plate element is between 0.8 inches and 3.0 inches. 11. The gas distribution plate assembly of claim 1, wherein the diffuser plate element is rectangular. 12. The gas distribution plate assembly of claim 11, wherein the diffuser plate element has a size of at least 1,200,000 square millimeters. 13. The gas distribution plate assembly of claim 1, wherein each gas channel further comprises: a first bore extending from the upstream side to the open bore, the first bore having a third diameter greater than the first diameter and a pointed, beveled, beveled or rounded bottom; and A pointed, beveled, beveled or rounded surface of the hollow cathode cavity is coupled to the open bore. 14. The gas distribution plate assembly of claim 1, wherein the open aperture is shaped to promote uniform flow of gas therethrough. 15. The gas distribution plate assembly of claim 1, wherein the open holes are evenly distributed among the inner and outer gas passages. 16. The gas distribution plate assembly of claim 1, wherein the open holes are unevenly distributed among the inner and outer gas passages. 17. A gas distribution plate assembly for a plasma processing chamber, comprising at least: a diffuser plate element having an upstream side and a downstream side; and Inner and outer gas channels, which are located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, The conical or cylindrical second diameter or depth or a combination of the two gradually increases from the center of the diffuser plate element to the edge, and the surface area density of the hollow cathode cavity of the inner gas channel is lower than that of the outer gas channel Surface area density of the hollow cathode cavity. 18. The gas distribution plate assembly of claim 17, wherein the second diameter is between 0.1 inch and 1.0 inch. 19. The gas distribution plate assembly of claim 17, wherein the second diameter is between 0.1 inch and 0.5 inch. 20. The gas distribution plate assembly of claim 17, wherein the conical or cylindrical shape has a depth between 0.1 inches and 2.0 inches. 21. The gas distribution plate assembly of claim 17, wherein the conical or cylindrical shape has a depth between 0.1 inch and 1.0 inch. 22. The gas distribution plate assembly as claimed in claim 17, wherein the conical expansion angle is between 10 degrees and 50 degrees. 23. The gas distribution plate assembly as claimed in claim 17, wherein the conical expansion angle is between 20 degrees and 40 degrees. 24. The gas distribution plate assembly of claim 17, wherein the second diameter is between 0.1 inch and 1.0 inch, the depth of the conical or cylindrical shape is between 0.1 inch and 2.0 inch, and The expansion angle of the conical shape is between 10° and 50°. 25. The gas distribution plate assembly of claim 17, wherein the spatial distance between the downstream ends of the hollow cathode cavities of adjacent gas channels is at most 0.6 inches. 26. The gas distribution plate assembly of claim 17, wherein the diffuser plate element has a thickness between 0.8 inches and 3.0 inches. 27. The gas distribution plate assembly of claim 17, wherein the diffuser plate element is rectangular. 28. The gas distribution plate assembly of claim 27, wherein the diffuser plate element has a size of at least 1,200,000 square millimeters. 29. The gas distribution plate assembly of claim 17, wherein each gas channel further comprises: a first bore extending from the upstream side to the open bore, the first bore having a third diameter greater than the first diameter and a pointed, beveled, beveled or rounded bottom; and A pointed, beveled, beveled or rounded surface of the hollow cathode cavity is coupled to the open bore. 30. The gas distribution plate assembly of claim 17, wherein the open aperture is shaped to promote uniform flow of gas therethrough. 31. The gas distribution plate assembly of claim 17, wherein the open holes are evenly distributed among said inner and outer gas passages. 32. The gas distribution plate assembly of claim 17, wherein the open holes are unevenly distributed among the inner and outer gas passages. 33. A gas distribution plate assembly for a plasma processing chamber comprising at least: a diffuser plate element having an upstream side and a downstream side; and a plurality of gas passages between the upstream side and the downstream side of the diffuser plate element, each gas passage having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open aperture and intersecting the downstream side of the diffuser plate element; said hollow cathode chamber having a conical or cylindrical shape and a diameter greater than said first diameter on said downstream side The second diameter, and the conical or cylindrical second diameter or depth or a combination of the two gradually increases from the center of the diffuser plate element to the edge, and the volume density of the hollow cathode cavity or the hollow cathode cavity The surface area density increases from the center to the edges of the diffuser plate element. 34. The gas distribution plate assembly of claim 33, wherein the surface area density of the hollow cathode cavities is between 10% and 100%. 35. The gas distribution plate assembly of claim 33, wherein the surface area density of the hollow cathode cavities is between 30% and 100%. 36. The gas distribution plate assembly of claim 33, wherein the second diameter is between 0.1 inch and 1.0 inch. 37. The gas distribution plate assembly of claim 33, wherein the second diameter is between 0.1 inches and 0.5 inches. 38. The gas distribution plate assembly of claim 33, wherein the conical or cylindrical shape has a depth between 0.1 inches and 2.0 inches. 39. The gas distribution plate assembly of claim 33, wherein the conical or cylindrical shape has a depth between 0.1 inch and 1.0 inch. 40. The gas distribution plate assembly as claimed in claim 33, wherein the conical expansion angle is between 10 degrees and 50 degrees. 41. The gas distribution plate assembly as claimed in claim 33, wherein the conical expansion angle is between 20 degrees and 40 degrees. 42. The gas distribution plate assembly of claim 33, wherein the second diameter is between 0.1 inches and 1.0 inches, the depth of the conical or cylindrical shape is between 0.1 inches and 2.0 inches, and The expansion angle of the conical shape is between 10° and 50°. 43. The gas distribution plate assembly of claim 33, wherein the diffuser plate element has a thickness between 0.8 inches and 3.0 inches. 44. The gas distribution plate assembly of claim 33, wherein the diffuser plate element is rectangular. 45. The gas distribution plate assembly of claim 44, wherein the diffuser plate element has a size of at least 1,200,000 square millimeters. 46. The gas distribution plate assembly of claim 33, wherein the open aperture is shaped to promote uniform flow of gas therethrough. 47. The gas distribution plate assembly of claim 33, wherein the open holes are evenly distributed among the plurality of gas channels. 48. The gas distribution plate assembly of claim 33, wherein the open holes are unevenly distributed among the plurality of gas channels. 49. A plasma processing chamber comprising at least: a diffuser plate element having an upstream side and a downstream side; an RF power source coupled to the diffuser element; Inner and outer gas channels, which are located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, The conical or cylindrical second diameter or depth or the combination of the two gradually increases from the center of the diffuser plate element to the edge, and the hollow cathode cavity of the inner gas channel is smaller than the hollow cathode cavity of the outer gas channel the size of the cavity; and A substrate support is adjacent the downstream side of the diffuser plate element. 50. The plasma processing chamber of claim 49, wherein the second diameter is between 0.1 inch and 1.0 inch. 51. The plasma processing chamber of claim 49, wherein the conical or cylindrical shape has a depth between 0.1 inches and 2.0 inches. 52. The plasma processing chamber of claim 49, wherein the conical shape has an expansion angle between 10 degrees and 50 degrees. 53. The plasma processing chamber of claim 49, wherein the second diameter is between 0.1 inch and 1.0 inch, the depth of the conical or cylindrical shape is between 0.1 inch and 2.0 inch, and The expansion angle of the conical shape is between 10° and 50°. 54. The plasma processing chamber of claim 49, wherein the spatial distance between the downstream ends of the hollow cathode cavities of adjacent gas passages is at most 0.6 inches. 55. The plasma processing chamber of claim 49, wherein the diffuser member has a thickness between 0.8 inches and 3.0 inches. 56. The plasma processing chamber of claim 49, wherein the diffuser member is rectangular. 57. The plasma processing chamber of claim 56, wherein the diffuser element has a size of at least 1,200,000 square millimeters. 58. The plasma processing chamber of claim 49, wherein each gas channel further comprises: a first bore extending from the upstream side to the open bore, the first bore having a third diameter greater than the first diameter and a pointed, beveled, beveled or rounded bottom; and A pointed, beveled, beveled or rounded surface of the hollow cathode cavity is coupled to the open bore. 59. The plasma processing chamber of claim 49, wherein the shape of the open hole promotes uniform flow of gas therethrough. 60. The plasma processing chamber of claim 49, wherein the open holes are uniformly distributed among the inner and outer gas passages. 61. The plasma processing chamber of claim 49, wherein the open holes are non-uniformly distributed among the inner and outer gas passages. 62. A plasma processing chamber comprising at least: a diffuser plate element having an upstream side and a downstream side; an RF power source coupled to the diffuser element; Inner and outer gas channels, which are located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, And the second diameter or depth of the conical or cylindrical shape or the combination of the two gradually increases from the center of the diffuser plate element to the edge, and the surface area density of the hollow cathode cavity of the inner gas passage is lower than that of the outer gas a surface area density of the hollow cathode cavity of the channel; and a substrate support adjacent the downstream side of the diffuser plate element. 63. The plasma processing chamber of claim 62, wherein the second diameter is between 0.1 inch and 1.0 inch. 64. The plasma processing chamber of claim 62, wherein the conical or cylindrical shape has a depth between 0.1 inches and 2.0 inches. 65. The plasma processing chamber of claim 62, wherein the conical shape has an expansion angle between 10 degrees and 50 degrees. 66. The plasma processing chamber of claim 62, wherein the second diameter is between 0.1 inches and 1.0 inches, the depth of the conical or cylindrical shape is between 0.1 inches and 2.0 inches, and The expansion angle of the conical shape is between 10° and 50°. 67. The plasma processing chamber of claim 62, wherein the spatial distance between the downstream ends of the hollow cathode cavities of adjacent gas passages is at most 0.6 inches. 68. The plasma processing chamber of claim 62, wherein the diffuser member has a thickness between 0.8 inches and 3.0 inches. 69. The plasma processing chamber of claim 62, wherein the diffuser member is rectangular. 70. The plasma processing chamber of claim 69, wherein the diffuser element has a size of at least 1,200,000 square millimeters. 71. The plasma processing chamber of claim 62, wherein each gas channel further comprises: a first bore extending from the upstream side to the open bore, the first bore having a third diameter greater than the first diameter and a pointed, beveled, beveled or rounded bottom; and A pointed, beveled, beveled or rounded surface of the hollow cathode cavity is coupled to the open bore. 72. The plasma processing chamber of claim 62, wherein the shape of the open hole promotes uniform flow of gas therethrough. 73. The plasma processing chamber of claim 62, wherein the open holes are uniformly distributed among the inner and outer gas passages. 74. The plasma processing chamber of claim 62, wherein the open holes are unevenly distributed among the inner and outer gas passages. 75. A plasma processing chamber comprising at least: a diffuser plate element having an upstream side and a downstream side; and an RF power source coupled to the diffuser element; A plurality of gas channels located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, The conical or cylindrical second diameter or depth or the combination of the two gradually increases from the center of the diffuser plate element to the edge, and the surface area density of the hollow cathode cavity of the plurality of gas passages is determined by the diffuser plate element gradually increases from the center to the periphery; and A substrate support is adjacent the downstream side of the diffuser plate element. 76. The plasma processing chamber of claim 75, wherein the surface area density of the hollow cathode cavities of the plurality of gas channels is between 10% and 100%. 77. The plasma processing chamber of claim 75, wherein the second diameter at the downstream end is between 0.1 inches and 1.0 inches. 78. The plasma processing chamber of claim 75, wherein the conical or cylindrical shape has a depth between 0.1 inches and 2.0 inches. 79. The plasma processing chamber of claim 75, wherein the cone has an expansion angle between 10 degrees and 50 degrees. 80. The plasma processing chamber of claim 75, wherein the second diameter is between 0.1 inches and 1.0 inches, the depth of the conical or cylindrical shape is between 0.1 inches and 2.0 inches, and The expansion angle of the conical shape is between 10° and 50°. 81. The plasma processing chamber of claim 75, wherein the diffuser member has a thickness between 0.8 inches and 3.0 inches. 82. The plasma processing chamber of claim 75, wherein the diffuser member is rectangular. 83. The plasma processing chamber of claim 82, wherein the diffuser element has a size of at least 1,200,000 square millimeters. 84. The plasma processing chamber of claim 75, wherein the shape of the open hole promotes uniform flow of gas therethrough. 85. The plasma processing chamber of claim 75, wherein the open holes are uniformly distributed among the plurality of gas channels. 86. The plasma processing chamber of claim 75, wherein the open holes are non-uniformly arranged among the plurality of gas channels. 87. A gas distribution plate assembly for a plasma processing chamber comprising at least: a diffuser plate element having an upstream side and a downstream side wherein the gas diffuser plate is divided into a plurality of coaxial regions; and A plurality of gas channels located between the upstream side and the downstream side of the diffuser plate element, each gas channel having: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and on said downstream side; said hollow cathode chamber having a conical or cylindrical shape and a second diameter greater than said first diameter on said downstream side, The conical or cylindrical second diameter or depth or the combination of the two gradually increases from the center of the diffuser plate element to the edge, the gas passages in each coaxial region are the same and the gas passages in each coaxial region The volume or surface area of the hollow cathode cavity of the channel gradually increases from the center to the edge of the diffuser plate element. 88. The gas distribution plate assembly of claim 87, wherein the hollow cathode cavity has a surface area density of between 10% and 100%. 89. The gas distribution plate assembly of claim 87, wherein the surface area density of the hollow cathode cavities is between 30% and 100%. 90. The gas distribution plate assembly of claim 87, wherein the second diameter is between 0.1 inch and 1.0 inch. 91. The gas distribution plate assembly of claim 87, wherein the conical or cylindrical shape at the downstream end has a depth between 0.1 inches and 2.0 inches. 92. The gas distribution plate assembly of claim 87, wherein the cone has an expansion angle between 10 degrees and 50 degrees. 93. The gas distribution plate assembly of claim 87, wherein the second diameter is between 0.1 inches and 1.0 inches, the depth of the conical or cylindrical shape is between 0.1 inches and 2.0 inches, and The expansion angle of the conical shape is between 10° and 50°. 94. The gas distribution plate assembly of claim 87 wherein the distance between hollow cathode cavities of adjacent gas passages at the downstream end is at most 0.6 inches. 95. The gas distribution plate assembly of claim 87, wherein the diffuser plate element has a thickness between 0.8 inches and 3.0 inches. 96. The gas distribution plate assembly of claim 87, wherein the diffuser plate element is rectangular. 97. The gas distribution plate assembly of claim 96, wherein the diffuser plate element has a size of at least 1,200,000 square millimeters. 98. The gas distribution plate assembly of claim 87, wherein the open aperture is shaped to promote uniform flow of gas therethrough. 99. The gas distribution plate assembly of claim 87, wherein the open holes are evenly distributed among the plurality of gas channels. 100. The gas distribution plate assembly of claim 87, wherein the open holes are unevenly distributed among the plurality of gas channels. 101. A diffuser plate, comprising: A main body has an upper surface and a bottom surface, the bottom surface is curved; A plurality of gas channels, which are located between the upper surface and the bottom surface, wherein each gas channel has: an open hole having a first diameter; and a hollow cathode chamber downstream of said open hole and intersecting said bottom surface; said hollow cathode chamber being conical or cylindrical in shape and a second diameter greater than said first diameter located on said downstream side diameter, the conical or cylindrical second diameter or depth or a combination of the two gradually increases from the center to the edge of the diffuser plate element, and the size of the hollow cathode cavity increases from the center to the edge of the diffuser plate element ;and An outer region and an inner region, wherein the body between the upper surface and the bottom surface of the outer region is thicker than the body between the upper surface and the bottom surface of the inner region. 102. The diffuser plate of claim 101, wherein the upper surface is flat. 103. The diffuser plate of claim 101, wherein the open aperture is shaped to promote uniform flow of gas therethrough. 104. The diffuser plate of claim 101, wherein the open holes are uniformly arranged among the plurality of gas passages. 105. The diffuser plate of claim 101, wherein the open holes are non-uniformly arranged among the plurality of gas passages.

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