Plasma uniformity control by gas diffuser hole design

Abstract

Embodiments of a gas diffuser plate for distributing gas in a processing chamber are provided. 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 and downstream sides of the diffuser plate. The gas passages include hollow cathode cavities at the downstream side to enhance plasma ionization. The depths, the diameters, the surface area and density of hollow cathode cavities of the gas passages that extend to the downstream end can be gradually increased from the center to the edge of the diffuser plate to improve the film thickness and property uniformity across the substrate. The increasing diameters, depths and surface areas from the center to the edge of the diffuser plate can be created by bending the diffuser plate toward downstream side, followed by machining out the convex downstream side. Bending the diffuser plate can be accomplished by a thermal process or a vacuum process. The increasing diameters, depths and surface areas from the center to the edge of the diffuser plate can also be created computer numerically controlled machining. Diffuser plates with gradually increasing diameters, depths and surface areas of the hollow cathode cavities from the center to the edge of the diffuser plate have been shown to produce improved uniformities of film thickness and film properties.

1 . A gas distribution plate assembly for a plasma processing chamber, comprising: 
 a diffuser plate having an upstream side, a downstream side, and has an array of gas passages passing between the upstream and downstream sides of the diffuser plate, wherein the array of gas passages has: 
 a first gas passage having a first hollow cathode cavity that is proximate to the downstream side, wherein the hollow cathode cavity has a wall that has first surface area; and  
 a second gas passage that is positioned closer to a center point of the diffuser plate than the first gas passage and has a second hollow cathode cavity that is proximate to the downstream side, wherein the second hollow cathode cavity has a wall that a second surface area and the second surface area is greater than the first surface area.  
   
   
   
       2 . The gas distribution plate assembly of  claim 1 , wherein the volume of the first hollow cathode cavity is less than the volume of the second hollow cathode cavity.  
   
   
       3 . The gas distribution plate assembly of  claim 1 , wherein the hollow cathode cavities are cone or cylinder shaped, and the cone or cylinder shaped hollow cathode cavities have a diameter formed at the downstream side and a depth.  
   
   
       4 . The gas distribution plate assembly of  claim 3 , wherein the diameter formed at the downstream side is between about 0.1 inch to about 1.0 inch.  
   
   
       5 . The gas distribution plate assembly of  claim 3 , wherein the depth is between about 0.1 inch to about 2.0 inch.  
   
   
       6 . The gas distribution plate assembly of  claim 3 , wherein the cones have a flaring angle that is between about 10 degrees to about 50 degrees.  
   
   
       7 . The gas distribution plate assembly of  claim 1 , wherein the hollow cathode cavities are cone shaped and the cone shaped cavities have: 
 a diameter formed at the downstream side that is between about 0.1 inch and about 1.0 inch;    a depth that is between about 0.1 inch and about 2.0 inch; and    a flaring angle of the cones are between about 10 degrees and about 50 degrees.    
   
   
       8 . The gas distribution plate assembly of  claim 1 , wherein a spacing between the downstream ends of the hollow cathode cavities of adjacent gas passages is at most about 0.6 inch.  
   
   
       9 . The gas distribution plate assembly of  claim 1 , wherein the diffuser plate is rectangular.  
   
   
       10 . The gas distribution plate assembly of  claim 1 , wherein the surface area of the downstream surface of the gas distribution plate is at least 1,200,000 mm 2 .  
   
   
       11 . The gas distribution plate assembly of  claim 3 , wherein the diameter or the lengths or a combination of both of the cones or cylinders gradually increases from center to edge of the diffuser plate.  
   
   
       12 . A gas distribution plate assembly for a plasma processing chamber, comprising: 
 a diffuser plate having an upstream side, a downstream side, and has an array of gas passages passing between the upstream and downstream sides of the diffuser plate, wherein the array of gas passages has: 
 a plurality of first gas passages having a first hollow cathode cavity that each have a first diameter that is in contact with the downstream side and a first depth; and  
 a plurality of second gas passages that are positioned closer to a center point of the diffuser plate than the plurality of first gas passages and each of the plurality of second gas passages have a second hollow cathode cavity that has a second diameter that is in contact with the downstream side and a second depth, wherein the second diameter is larger than the first diameter or the second depth is larger than the first depth.  
   
   
   
       13 . The gas distribution plate assembly of  claim 12 , wherein the diffuser plate is rectangular.  
   
   
       14 . The gas distribution plate assembly of  claim 12 , wherein the surface area of the downstream surface of the gas distribution plate is at least 1,200,000 mm 2 .  
   
   
       15 . A gas distribution plate assembly for a plasma processing chamber, comprising: 
 a diffuser plate having an upstream side, a downstream side, and has an array of gas passages passing between the upstream and downstream sides of the diffuser plate, wherein the array of gas passages has: 
 a plurality of first gas passages having a first hollow cathode cavity that each have a first diameter that is in contact with the downstream side, a first flaring angle, and a first depth; and  
 a plurality of second gas passages that have a second hollow cathode cavity that has a second diameter that is in contact with the downstream side, a second flaring angle and a second depth, wherein the second diameter is greater than the first diameter, the second flaring angle is greater than the first flaring angle, or the second depth is greater than the first depth.  
   
   
   
       16 . The gas distribution plate assembly of  claim 15 , wherein the diffuser plate is rectangular.  
   
   
       17 . The gas distribution plate assembly of  claim 15 , wherein the surface area of the downstream surface of the gas distribution plate is at least 1,200,000 mm 2 .  
   
   
       18 . The gas distribution plate assembly of  claim 15 , wherein the first and second diameters are between about 0.1 inch and about 1.0 inch in size.  
   
   
       19 . The gas distribution plate assembly of  claim 15 , wherein the first and second depths are between about 0.1 inch and about 2.0 inch.  
   
   
       20 . The gas distribution plate assembly of  claim 15 , wherein the first and second flaring angles are between about 10 degrees to about 50 degrees.