Plasma processing device

Abstract

In a microwave plasma processing apparatus, the reflection of microwave by the joint unit between the microwave supplying waveguide and the microwave antenna is reduced by providing a taper surface or a member having a medium permittivity between the microwave supplying waveguide and the microwave antenna so as to moderate an impedance change. Accordingly, the efficiency of power supplying is improved, and reduced discharge ensures stable formation of plasma.

What is claimed is:  
     
         1 . A plasma processing apparatus, comprising: 
 a processing vessel defined by an outer wall and having a stage for holding a substrate to be processed;    an evacuation system coupled to said processing vessel;    a microwave transparent window provided on said processing vessel as a part of said outer wall, and opposite said substrate held on said stage;    a plasma gas supplying part for supplying plasma gas to said processing vessel;    a microwave antenna provided on said processing vessel in correspondence to said microwave; and    a microwave power source electrically coupled to said microwave antenna,    wherein 
 said microwave antenna comprising 
 a coaxial waveguide connected to said microwave power source, said coaxial waveguide having an inner conductor core and an outer conductor tube surrounding said inner conductor core, and  
 an antenna body provided to a point of said coaxial waveguide;  
 said antenna body further comprising 
 a first conductor surface forming a microwave radiation surface coupled with said microwave transparent window, and  
 a second conductor surface opposite said first conductor surface via a dielectric plate, said second conductor surface being connected to said first conductor surface at a peripheral part of said dielectric plate;  
 said inner conductor core is connected to said first conductor surface by a first joint unit;  
 said outer conductor tube is connected to said second conductor surface by a second joint unit;  
 said first joint unit forms a first taper unit in which an outer diameter of said inner conductor core increases toward said first conductor surface; and  
 said second joint unit forms a second taper unit in which an inner diameter of said outer conductor tube increases toward said first conductor surface.  
 
 
   
     
     
         2 . The microwave plasma processing apparatus as claimed in  claim 1 , wherein the distance between an outer surface of said inner conductor core and an inner surface of said outer conductor tube increases toward said first conductor surface.  
     
     
         3 . The microwave plasma processing apparatus as claimed in  claim 1 , wherein 
 said first taper unit is defined by a first curved surface; and    said second taper unit is defined by a second curved surface.    
     
     
         4 . The microwave plasma processing apparatus as claimed in  claim 1 , further comprising a dielectric member provided in a space between said inner conductor core and said outer conductor tube, defined by a first edge face and a second edge face opposing said first edge face, said first edge face being adjacent to said dielectric plate, a permittivity of said dielectric member being lower than a permittivity of said dielectric plate and higher than a permittivity of air.  
     
     
         5 . The microwave plasma processing apparatus as claimed in  claim 4 , wherein composition of said dielectric member is changed from said first edge face to said second edge face.  
     
     
         6 . The microwave plasma processing apparatus as claimed in  claim 4 , wherein 
 said dielectric plate is made of either alumina, silicon oxide, silicon oxynitrided, or silicon nitrided; and    said dielectric member is made of silicon oxide.    
     
     
         7 . The microwave plasma processing apparatus as claimed in  claim 4 , further comprising another dielectric member in a space between said inner conductor core and said outer conductor tube, adjacent to said second edge face of said dielectric member, a permittivity of said other dielectric member being lower than a permittivity of said dielectric member and higher than a permittivity of air.  
     
     
         8 . The microwave plasma processing apparatus as claimed in  claim 7 , wherein said dielectric member is made of silicon oxide, and said other dielectric member is made of Teflon.  
     
     
         9 . The microwave plasma processing apparatus as claimed in  claim 4 , wherein 
 said second edge face of said dielectric member forms a taper surface; and    an outer diameter of said dielectric member decreases as a distance from said first edge face increases.    
     
     
         10 . The microwave plasma processing apparatus as claimed in  claim 9 , wherein an outer diameter of said dielectric member linearly decreases as a distance from said first edge face increases.  
     
     
         11 . The microwave plasma processing apparatus as claimed in  claim 9 , wherein an outer diameter of said dielectric member exponentially decreases as a distance from said first edge face increases.  
     
     
         12 . The microwave plasma processing apparatus as claimed in  claim 1 , wherein said plasma gas supplying part further comprises a plasma gas passage connectable to a plasma gas source, said plasma gas passage being made of a microwave-transparent material, and a shower plate having a plurality of openings in communication with said plasma gas passage, provided in an interior of said microwave transparent window in intimate contact.  
     
     
         13 . The microwave plasma processing apparatus as claimed in  claim 12 , wherein said shower plate is made of alumina.  
     
     
         14 . The microwave plasma processing apparatus as claimed in  claim 1 , wherein said plasma gas supplying part is provided in an outer wall of said processing vessel.  
     
     
         15 . The microwave plasma processing apparatus as claimed in  claim 14 , wherein said plasma gas supplying part is tubes provided in said outer wall of said processing vessel.  
     
     
         16 . The plasma processing apparatus as claimed in  claim 1 , wherein said microwave antenna is provided so that said first conductor surface touches said microwave transparent window.  
     
     
         17 . The plasma processing apparatus as claimed in  claim 1 , wherein said microwave antenna is provided so that said first conductor surface is spaced from said microwave transparent window.  
     
     
         18 . The plasma processing apparatus as claimed in  claim 1 , wherein 
 a processing gas source is provided between said substrate and said plasma gas supplying part, in said processing vessel, said processing gas supplying part opposing to said substrate;    a first opening through which plasma formed in said processing vessel passes and a second opening through which processing gas is provided; and    said second opening is in communication with a processing gas passage connected to a processing gas source, formed in said processing gas supplying source.    
     
     
         19 . A plasma processing apparatus, comprising: 
 a processing vessel defined by an outer wall and having a stage for holding a substrate to be processed;    an evacuation system coupled to said processing vessel;    a microwave transparent window provided on said processing vessel as a part of said outer wall, opposite said substrate held on said stage;    a plasma gas supplying part for supplying plasma gas to said processing vessel;    a microwave antenna provided on said processing vessel in correspondence to said microwave; and    a microwave power source electrically coupled to said microwave antenna,    wherein 
 said microwave antenna comprising 
 a coaxial waveguide connected to said microwave power source, said coaxial waveguide having an inner conductor core and an outer conductor tube surrounding said inner conductor core, and  
 an antenna body provided to a point of said coaxial waveguide;  
 said antenna body further comprising 
 a first conductor surface forming a microwave radiation surface coupled with said microwave transparent window, and  
 a second conductor surface opposite said first conductor surface via a dielectric plate, said second conductor surface being connected to said first conductor surface at a peripheral part of said dielectric plate;  
 said inner conductor core is connected to said first conductor surface by a first joint unit;  
 said outer conductor tube is connected to said second conductor surface by a second joint unit;  
 a dielectric member is provided in a space between said inner conductor core and said outer conductor tube, defined by a first edge face and a second edge face opposing said first edge face, said first edge face being adjacent to said dielectric plate, a permittivity of said dielectric member being lower than a permittivity of said dielectric plate and higher than a permittivity of air.  
 
 
   
     
     
         20 . The plasma processing apparatus as claimed in  claim 19 , wherein said inner conductor core is connected substantially perpendicularly to said first conductor surface in said first joint unit.  
     
     
         21 . The plasma processing apparatus as claimed in  claim 19 , wherein, in said second joint unit, said outer conductor core is connected substantially perpendicularly to said second conductor surface.  
     
     
         22 . The plasma processing apparatus as claimed in  claim 19 , wherein composition of said dielectric member changes from said first edge face to said second edge face.  
     
     
         23 . The plasma processing apparatus as claimed in  claim 19 , wherein 
 said dielectric plate is made of either alumina, silicon oxide, silicon oxynitridated, or silicon nitridated; and    said dielectric member is made of silicon oxide.    
     
     
         24 . The plasma processing apparatus as claimed in  claim 21 , wherein, in a space between said inner conductor core and said outer waveguide, another dielectric member having a permittivity lower than a permittivity of said dielectric member and higher than a permittivity of air is provided adjacent to said second edge face of said dielectric member.  
     
     
         25 . The plasma processing apparatus as claimed in  claim 24 , wherein said dielectric member is made of silicon oxide, and said other dielectric member is made of Teflon.  
     
     
         26 . The plasma processing apparatus as claimed in  claim 21 , wherein said second edge face of said dielectric member forms a taper surface, and an outer diameter of said dielectric member decreases as a distance from said first edge face increases.  
     
     
         27 . The plasma processing apparatus as claimed in  claim 26 , wherein an outer diameter of said dielectric member decreases linearly as a distance from said first edge face increases.  
     
     
         28 . The plasma processing apparatus as claimed in  claim 26 , wherein an outer diameter of said dielectric member decreases exponentially as a distance from said first edge face increases.  
     
     
         29 . The plasma processing apparatus as claimed in  claim 19 , wherein said plasma gas supplying part is provided with a plasma gas passage connectible to a plasma gas source, made of a microwave transparent material, and a shower plate having a plurality of openings in communication with said plasma gas passage.  
     
     
         30 . The plasma processing apparatus as claimed in  claim 29 , wherein said microwave transparent window and said shower plate are made of alumina.  
     
     
         31 . The plasma processing apparatus as claimed in  claim 19 , wherein said plasma gas supplying part is provided in an outer wall of said processing vessel.  
     
     
         32 . The plasma processing apparatus as claimed in  claim 31 , wherein said plasma gas supplying part is tubes provided in said processing vessel.  
     
     
         33 . The plasma processing apparatus as claimed in  claim 19 , wherein said microwave antenna is provided so that said first conductor surface touches said microwave transparent window.  
     
     
         34 . The plasma processing apparatus as claimed in  claim 19 , wherein said microwave antenna is provided so that said first conductor surface separates from said microwave transparent window.  
     
     
         35 . The plasma processing apparatus as claimed in  claim 19 , wherein a process gas supplying part is provided between said substrate and said plasma gas supplying part in said processing vessel, said process gas supplying part opposing to said substrate; 
 a first opening through which plasma gas formed in said processing vessel passes and a second opening through which process gas is supplied are formed in said process gas supplying part; and    said second opening is connected to a process gas passage formed in said process gas supplying part and connected to a process gas source.