Plasma processing apparatus capable of suppressing variation of processing characteristics

Abstract

A plasma processing apparatus includes a reaction container with the inner side wall thereof insulated, a sample rest and an antenna arranged in the reaction container. The high-frequency power is supplied to the antenna from a plasma generating power supply, the processing gas is introduced into the reaction container and converted to a plasma, and the sample placed on the sample rest is processed by the plasma. A matching unit for securing the impedance matching is inserted between the plasma generating power supply and a load circuit including the antenna. The matching unit includes a sensor for measuring the impedance characteristic on the load circuit side and a unit for changing the match point and the matching track leading to the match point on the input side of the matching unit in accordance with the measurement by the sensor.

1 . A plasma processing apparatus comprising: 
 a reaction container with the inner side wall insulated and having arranged therein a sample rest and an antenna supplied with high-frequency power from a plasma generating power supply, wherein the processing gas introduced into said reaction container is converted into a plasma thereby to process a sample on said sample rest with said plasma; and    a matching unit for impedance matching between said plasma generating power supply and a load circuit including said antenna;    wherein said matching unit includes a sensor for measuring the impedance characteristics of said load circuit, and a means for changing the match point and the matching track leading to said match point as viewed from the input terminal of said matching unit in accordance with the measurement of said sensor.    
   
   
       2 . A plasma processing apparatus according to  claim 1 , further comprising a means for issuing an alarm when the change in the impedance characteristic value measured by said sensor exceeds a predetermined value.  
   
   
       3 . A plasma processing apparatus according to  claim 1 , further comprising a means for determining selected one of the wear of the protective coating on the inner side wall of the reaction container and the cutoff of the quartz part in the upper portion of the reaction container based on the direction in which the impedance characteristic value measured by said sensor changes.  
   
   
       4 . A plasma processing apparatus according to  claim 1 , 
 wherein the matching track leading to the match point is set in such a manner as to avoid the unstable area of the plasma.    
   
   
       5 . A plasma processing apparatus according to  claim 4 , 
 wherein said matching unit includes a data base for storing the data indicating the unstable area of the plasma as a range of the input voltage reflection coefficient.    
   
   
       6 . A plasma processing apparatus according to  claim 1 , 
 wherein the high-frequency power from said plasma-generating power supply is supplied to said sample rest so that said sample rest functions as an antenna.    
   
   
       7 . A plasma processing apparatus according to  claim 1 , 
 wherein the impedance characteristic on the load circuit side measured by said sensor is a load power reflection coefficient, and the match point on the Smith chart of the input voltage reflection coefficient is shifted in accordance with the shift on the Smith chart of the load power reflection coefficient.    
   
   
       8 . A plasma processing apparatus according to  claim 7 , further comprising a data base for storing the correspondence between the direction and amount of the shift on the Smith chart of the load power reflection coefficient on the one hand and the direction and amount of the shift of the match point on the Smith chart of the input voltage reflection coefficient on the other hand.  
   
   
       9 . A plasma processing apparatus according to  claim 1 , further comprising a means for adjusting the machining size by changing the match point on the Smith chart of the input voltage reflection coefficient.