Plasma processing apparatus with reduced parasitic capacity and loss in RF power

Abstract

A plasma processing apparatus comprises a grounded housing, a thin RF plate electrode, an opposite electrode facing the RF plate electrode, and a RF power source for applying a radio frequency to either the RF plate electrode or the opposite electrode to produce plasma between the two electrodes. If the radio frequency applied to the electrode is f (MHz), the parasitic capacity C (pF) between the grounded portion of the housing and a conductive portion through which the radio frequency propagates is less than 1210*f −0.9 . The thickness of the RF plate electrode is 1 mm to 6 mm, and it is supported by a heat sink. The heat sink has a coolant passage in the proximity to the RF plate electrode. The heat sink also has a groove or a cavity in addition to the coolant passage, thereby reducing the value of the dielectric constant of the heat sink as a whole.

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         10 . A plasma processing apparatus comprising: 
 a grounded housing;    an RF plate electrode placed in the housing;    an opposite electrode facing the RF plate electrode; and    first and second radio-frequency power sources for applying different values of radio frequencies to either the RF plate electrode or the opposite electrode, one of the radio frequencies being 60 MHz or higher, which is represented as f(MHz), wherein the parasitic capacity C (pF) between the grounded portion of the housing and a conductive portion through which the radio frequencies propagate is less than 1210*f −0.9 .    
     
     
         11 . The plasma processing apparatus of  claim 10 , further comprising a heat sink that holds the RF plate electrode and has a coolant passage in proximity to the RF plate electrode.  
     
     
         12 . The plasma processing apparatus of  claim 11 , wherein the heat sink further has a groove inside it.  
     
     
         13 . The plasma processing apparatus of  claim 11 , wherein the heat sink further has a cavity.  
     
     
         14 . The plasma processing apparatus of  claim 11 , wherein the heat sink is supported by a part of the housing, and a shock absorber is inserted between the heat sink and said part of the housing.  
     
     
         15 . The plasma processing apparatus of  claim 14 , wherein the heat sink is made of a ceramic material and the shock absorber is a malleable insulator.  
     
     
         16 . The plasma processing apparatus of  claim 14 , wherein the shock absorber is made of Teflon.  
     
     
         17 . A plasma processing apparatus comprising: 
 a grounded housing;    a wafer mount electrode placed in the housing and having at least two holes penetrating it, the wafer mount electrode including an RF plate electrode having a thickness of 6 mm or less and an insulator for supporting the RF plate electrode;    an opposite electrode facing the wafer mount electrode;    an RF power source for applying a radio frequency to either the wafer mount electrode or the opposite electrode to generate plasma between the two electrodes; and    pusher pins inserted in the holes and movable between a first position, at which the pusher pins project out of the wafer mount electrode in order to receive a wafer, and a second position, at which the pusher pins retreat below the RF plate electrode during the generation of plasma.    
     
     
         18 . The plasma processing apparatus of  claim 17 , wherein the stroke of the pusher pins between the first and second positions is twice or more of the thickness of the RF plate electrode.  
     
     
         19 . The plasma processing apparatus of  claim 17 , further comprising a heat sink for holding the wafer mount electrode, wherein the insulator is a part of or the entirety of the heat sink, and the heat sink has at least one of a coolant passage, a groove, and a cavity.  
     
     
         20 . The plasma processing apparatus of  claim 19 , wherein the heat sink is supported by a part of the housing, and a shock absorber is inserted between the heat sink and said portion of the housing.  
     
     
         21 . The plasma processing apparatus of  claim 17 , wherein if the radio frequency applied to the electrode is f (MHz), the parasitic capacity C (pF) between the grounded portion of the housing and a conductive portion through which the radio frequency propagates is less than 1210*f −0.9 .  
     
     
         22 . The plasma processing apparatus of  claim 17 , wherein the pusher pins are made of a conductor or a semiconductor.  
     
     
         23 . A plasma processing apparatus comprising: 
 a wafer mount electrode;    an opposite electrode facing the wafer mount electrode;    a DC power source for supplying a direct-current voltage in order to hold a wafer on the wafer mount electrode in an electrostatic manner;    an RF power source for applying a radio frequency to either the wafer mount electrode or the opposite electrode to generate plasma between the two electrodes; and    a radio-frequency trap positioned between the wafer mount electrode and the DC power source, the radio-frequency trap having an electrical length of (2 n+1)/4 wavelength of the applied radio frequency.    
     
     
         24 . The plasma processing apparatus of  claim 23 , wherein the radio-frequency trap is a conductive pipe.  
     
     
         25 . The plasma processing apparatus of  claim 23 , wherein the physical length of the radio-frequency trap is set shorter than (2 n+1)/4 wavelength of the applied radio frequency taking into account parasitic capacity of the plasma processing apparatus and inductance of transmission lines.  
     
     
         26 . The plasma processing apparatus of  claim 23 , further comprising a bypass capacitor connected in parallel with the DC power source; 
 wherein one end of the radio-frequency trap is connected to the wafer mount electrode, and the other end of the radio-frequency trap is connected to the DC power source and the bypass capacitor.    
     
     
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