Plasma processing apparatus and power supply control method

Abstract

A plasma processing apparatus includes: a placement table serving as a lower electrode and configured to place thereon a workpiece to be subjected to a plasma processing; a DC power supply configured to alternately generate a positive DC voltage and a negative DC voltage to be applied to the placement table; and a controller configured to control an overall operation of the plasma processing apparatus. The controller is configured to: measure a voltage of the workpiece placed on the placement table; calculate, based on the measured voltage of the workpiece, a potential difference between the placement table and the workpiece in a period during which the negative DC voltage is applied to the placement table; and control the DC power supply such that a value of the negative DC voltage applied to the placement table is shifted by a shift amount that decreases the calculated potential difference.

1 . A plasma processing apparatus comprising:
 a chamber;   a substrate support disposed in the chamber;   a bias electrode disposed in the substrate support;   a DC voltage source electrically connected to the bias electrode and configured to apply a pulsed DC voltage to the bias electrode; and   a controller configured to perform
 a first process to calculate a potential difference between a wafer disposed on the substrate support and the bias electrode during a period in which a low level of the pulsed DC voltage is applied to the bias electrode, 
 a second process to determine whether the potential difference exceeds a predetermined threshold, and 
 a third process to adjust a parameter of the pulsed DC voltage. 
   
     
     
         2 . The plasma processing apparatus according to  claim 1 ,
 wherein the controller is configured to shift a voltage level of the pulsed DC voltage in the third process when the potential difference is equal or exceeds the predetermined threshold in the second process.   
     
     
         3 . The plasma processing apparatus according to  claim 2 ,
 wherein the controller is configured to shift a voltage level of the pulsed DC voltage to decrease the potential difference in the third process.   
     
     
         4 . The plasma processing apparatus according to  claim 1 ,
 wherein the controller is further configured to perform a fourth process to determine whether an adjustment of a duty ratio of the pulsed DC voltage is requested when the potential difference is less than the predetermined threshold in the second process.   
     
     
         5 . The plasma processing apparatus according to  claim 4 ,
 wherein the controller is configured to adjust the duty ratio of the pulsed DC voltage when the adjustment of the duty ratio of the pulsed DC voltage is requested in the fourth process.   
     
     
         6 . The plasma processing apparatus according to  claim 1 ,
 wherein the controller is further configured to perform a fifth process to determine whether an adjustment of an amplitude of the pulsed DC voltage is requested when the potential difference is less than the predetermined threshold in the second process.   
     
     
         7 . The plasma processing apparatus according to  claim 6 ,
 wherein the controller is configured to adjust the amplitude of the pulsed DC voltage when the adjustment of the amplitude of the pulsed DC voltage is requested in the fifth process.   
     
     
         8 . The plasma processing apparatus according to  claim 1 ,
 wherein the controller is further configured to perform a sixth process to determine whether an adjustment of a frequency of the pulsed DC voltage is requested when the potential difference is less than the predetermined threshold in the second process.   
     
     
         9 . The plasma processing apparatus according to  claim 8 ,
 wherein the controller is configured to adjust the frequency of the pulsed DC voltage when the adjustment of the frequency of the pulsed DC voltage is requested in the sixth process.   
     
     
         10 . The plasma processing apparatus according to  claim 1 ,
 wherein a low pass filter is disposed between the bias electrode and the DC voltage source.   
     
     
         11 . The plasma processing apparatus according to  claim 4 ,
 wherein a low pass filter is disposed between the bias electrode and the DC voltage source.   
     
     
         12 . The plasma processing apparatus according to  claim 6 ,
 wherein a low pass filter is disposed between the bias electrode and the DC voltage source.   
     
     
         13 . The plasma processing apparatus according to  claim 8 ,
 wherein a low pass filter is disposed between the bias electrode and the DC voltage source.   
     
     
         14 . A plasma processing apparatus, comprising:
 a chamber;   a substrate support disposed in the chamber;   a bias electrode disposed in the substrate support;   a DC voltage source configured to apply a pulsed DC voltage to the bias electrode, the pulsed DC voltage having a first voltage level during a first period and a second voltage level during a second voltage level, the first period and the second period being repeated in alternating manner, the first voltage level being greater than the second voltage level; and   a controller configured to adjust the second voltage level based on a potential difference between a substrate disposed on the substrate support and the bias electrode during the second period to decrease the potential difference.