Method and apparatus for improved plasma processing uniformity

Abstract

A method and apparatus for generating and controlling a plasma ( 130 ) formed in a capacitively coupled plasma system ( 100 ) having a plasma electrode ( 140 ) and a bias electrode in the form of a workpiece support member ( 170 ), wherein the plasma electrode is unitary and has multiple regions (R i ) defined by a plurality of RF power feed lines ( 156 ) and the RF power delivered thereto. The electrode regions may also be defined as electrode segments ( 420 ) separated by insulators ( 426 ). A set of process parameters A={n, τ i , Φ i , P i , S; L i } is defined, herein n is the number of RF feed lines connected to the electrode upper surface at locations L i , τ i is the on-time of the RF power for the i th RF feed line, Φ i is the phase of the i th RF feed line relative to a select one of the other RF feed lines, P i is the RF power delivered to the electrode through the i th RF feed line at location L i , and S is the sequencing of RF power to the electrode through the RF feed lines. One or more of these parameters are adjusted so that operation of the plasma system results in a workpiece ( 176 ) being processed with a desired amount or degree of process uniformity.

What is claimed is:  
     
         1 . An electrode apparatus for use in plasma processing, comprising: 
 a) a unitary electrode;    b) a RF power supply; and    c) a RF multiplexer electrically connected to said RF power supply and to a plurality of locations on said unitary electrode via a corresponding plurality of RF feed lines thereby establishing a plurality of electrode regions corresponding to said plurality of RF feed lines.    
     
     
         2 . An apparatus according to  claim 1 , further comprising a plurality of match networks arranged one in each of said plurality of RF feed lines.  
     
     
         3 . An apparatus according to  claim 2 , further including a control system electrically connected for controlling the operation of said RF power supply and said RF multiplexer.  
     
     
         4 . A plasma reactor system for processing a workpiece, comprising: 
 a) a plasma chamber having sidewalls, an upper wall and a lower wall defining an interior region capable of supporting a plasma;    b) a unitary electrode having a plurality of electrode regions, arranged within said interior region adjacent said upper wall;    c) a RF multiplexer electrically connected to the plurality of electrode regions of said unitary electrode via a corresponding plurality of RF feed lines;    d) corresponding to said plurality of RF feed lines; and    e) a workpiece support member, arranged in the interior region adjacent said lower wall, for supporting the workpiece.    
     
     
         5 . A system according to  claim 4 , further comprising: 
 f) a control system electrically connected to said RF multiplexer, for controlling the operation of said RF multiplexer when processing the workpiece.    
     
     
         6 . A system according to  claim 5 , further comprising: 
 g) a plurality of match networks each arranged one in a respective one of said plurality of RF feed lines.    
     
     
         7 . A system according to  claim 6 , further comprising: 
 h) a gas supply system in pneumatic communication with said chamber interior region, for supplying gas to said chamber interior region.    
     
     
         8 . A system according to  claim 7 , further comprising: 
 i) a workpiece support member RF power supply electrically connected to said workpiece support member, for electrically biasing said workpiece support member.    
     
     
         9 . A system according to  claim 8 , further comprising: 
 j) a vacuum system pneumatically connected to said chamber interior region.    
     
     
         10 . A system according to  claim 9 , further comprising: 
 k) a workpiece handling system in operative communication with said workpiece support member, for providing the workpiece to the workpiece support member.    
     
     
         11 . A system according to  claim 5 , further including a database electrically connected to said control system.  
     
     
         12 . A method of determining a set of optimum plasma process parameters A*={n*, τ i *, Φ i *, P i *, S*; L i *} for plasma processing, with a high degree of uniformity, a workpiece in a plasma reactor chamber having an electrode with an upper surface as part of a plasma reactor system, wherein n is the number of RF feed lines connected to the electrode upper surface at locations L i , t i  is the on-time of the RF power for the i th  RF feed line, Φ i  is the phase of the i th  RF feed line relative to a select one of the other RF feed lines, Pi is the RF power delivered to the electrode to location L i  through the i th  RF feed line, and S is the sequencing of RF power to the electrode through the RF feed lines, the method comprising the steps of: 
 a) setting initial values for process parameters n, τ i , Φ i , P i , and S; and  
 b) processing one or more workpieces while varying one or more of said process parameters to determine the optimized set of process parameters A*={n*, τ i *, Φ i *, P i *, S*} that achieve a process non-uniformity less than a predetermined standard.  
 
     
     
         13 . A method according to  claim 12 , wherein said step b) includes the steps of: 
 i) forming a first plasma within the reactor chamber having characteristics corresponding to said process parameters and processing a first workpiece for a predetermined process time;    ii) measuring the workpiece process uniformity; and    iii) comparing the workpiece process uniformity to a predetermined standard.    
     
     
         14 . A method according to  claim 13 , wherein said step b) further includes the step of: 
 iv) reducing the workpiece process non-uniformity by changing at least one of said process parameters and repeating said steps i) through iii) using one of said first workpiece and a workpiece other than said first workpiece, until the workpiece process non-uniformity is less than said predetermined standard.    
     
     
         15 . A method according to  claim 12 , wherein in said steps a) and b), the locations L i  of the RF feed lines are parameters in the set A of process parameters that can be varied.  
     
     
         16 . A method according to  claim 12 , wherein the initial process parameter values are determined with the assistance of computer modeling.  
     
     
         17 . A method according to  claim 12 , wherein said step b) includes use of a linear processing model as a basis for varying at least one of the process parameters.  
     
     
         18 . A method according to  claim 12 , wherein said step b) includes use of a nonlinear processing model as a basis for varying at least one of the process parameters.  
     
     
         19 . A method according to  claim 12 , wherein said step b) includes providing RF power P i  to a plurality of electrode segments in a multi-segment electrode by multiplexing RF power via RF power multiplexing.  
     
     
         20 . A method according to  claim 19 , wherein said RF power multiplexing is accomplished by programming a control system electrically connected to a plurality of RF power supplies and electronically controlling the activation of the RF power supplies.  
     
     
         21 . A method according to  claim 12 , wherein said step b) involves providing RF power P i  to a unitary electrode via RF power multiplexing.  
     
     
         22 . A method of processing a workpiece to be processed according to  claim 12 , further including the steps, after said step b), of: 
 c) providing the workpiece to be processed in the reactor chamber;    d) forming an optimized plasma with the process chamber using the set of optimized process parameters determined in said step b); and    e) processing the workpiece to be processed with the optimized plasma.    
     
     
         23 . A method of determining a set of optimum plasma process parameters A*={n*, τ i *, Φ i *, P i *, S*; L i *} for plasma processing, with a desired degree of uniformity, a workpiece in a plasma reactor chamber having an electrode with an upper surface as part of a plasma reactor system, wherein n is the number of RF feed lines connected to the electrode upper surface at locations L i , τ i  is the on-time of the RF power for the i th  RF feed line, τ i  is the phase of the i th  RF feed line relative to a select one of the other RF feed lines, P i  is the RF power delivered to the electrode to location L i  through the i th  RF feed line, and S is the sequencing of RF power to the electrode through the RF feed lines, the method comprising the steps of: 
 a) setting initial values for process parameters n, τ i , Φ i , P i , and S; and  
 b) processing one or more workpieces while varying one or more of said process parameters to determine the optimized set of process parameters A*={n*, τ i *, Φ i *, P i , S} that achieve a desired process uniformity.  
 
     
     
         24 . A method according to  claim 23 , wherein said step b) includes the steps of: 
 i) forming a first plasma within the reactor chamber having characteristics corresponding to said process parameters and processing a first workpiece for a predetermined process time;    ii) measuring the workpiece process uniformity; and    iii) comparing the workpiece process uniformity to a predetermined standard.    
     
     
         25 . A method according to  claim 23 , wherein said step b) further includes the step of: 
 iv) reducing the workpiece process non-uniformity by changing at least one of said process parameters and repeating said steps i) through iii) using one of said first workpiece and a workpiece other than said first workpiece, until the workpiece process non-uniformity is less than said predetermined standard.    
     
     
         26 . A method of processing a workpiece to be processed according to  claim 23 , further including the steps, after said step b), of: 
 c) providing the workpiece to be processed in the reactor chamber;    d) forming an optimized plasma with the process chamber using the set of optimized process parameters determined in said step b); and    e) processing the workpiece to be processed with the optimized plasma.