Etching method and plasma processing apparatus

Abstract

A disclosed etching method includes (a) generating plasma of a processing gas in a chamber of a plasma processing apparatus. The plasma is generated in a state where a substrate is placed on a substrate support having a lower electrode in the chamber. The substrate has a film and a mask. The mask is provided on the film. The etching method further includes (b) etching the film by supplying ions from the plasma to the substrate by periodically applying a pulse of a voltage to a lower electrode. In the operation (b), a level of a voltage of the pulse is changed at least once such that an absolute value of a negative potential of the substrate has a tendency to increase according to progress of etching of the film.

What is claimed is: 
     
         1 . A plasma processing apparatus comprising:
 a chamber;   a substrate support having a lower electrode and provided in the chamber;   a gas supply configured to supply a processing gas into the chamber;   a plasma generator configured to generate plasma from a gas in the chamber;   a bias power source electrically connected to the lower electrode and configured to periodically generate a pulse of a voltage; and   a controller configured to control the gas supply, the plasma generator, and the bias power source,   wherein the controller is configured to
 (a) control the gas supply and the plasma generator to generate plasma of the processing gas in the chamber, and 
 (b) control the bias power source to periodically apply the pulse to the lower electrode to supply ions from the plasma to a substrate on the substrate support, thereby etching a film of the substrate, and 
   in said (b), the bias power source is controlled to change a level of a voltage of the pulse at least once such that an absolute value of a negative potential of the substrate has a tendency to increase according to progress of etching of the film.   
     
     
         2 . The plasma processing apparatus according to  claim 1 , wherein the bias power source is configured to generate, as the pulse, a pulse of a negative voltage or a pulse of a negative direct-current voltage, and to increase an absolute value of the voltage of the pulse at least once such that the absolute value of the voltage of the pulse has a tendency to increase according to the progress of the etching of the film, in said (b). 
     
     
         3 . The plasma processing apparatus according to  claim 1 , wherein the bias power source is configured to set a duty ratio of the pulse to 20% or less, in said (b). 
     
     
         4 . The plasma processing apparatus according to  claim 1 , wherein the bias power source is configured to decrease a duty ratio of the pulse at least once such that the duty ratio of the pulse has a tendency to decrease according to the progress of the etching of the film, in said (b). 
     
     
         5 . The plasma processing apparatus according to  claim 4 , wherein the bias power source is configured to decrease the duty ratio of the pulse such that the duty ratio of the pulse has a ratio of 15% or more and 20% or less, in said (b). 
     
     
         6 . The plasma processing apparatus according to  claim 4 , wherein the bias power source is configured to reduce the duty ratio of the pulse stepwise or gradually, in said (b). 
     
     
         7 . The plasma processing apparatus to  claim 1 , wherein the bias power source is configured to change the level of the voltage of the pulse stepwise or gradually, in said (b). 
     
     
         8 . A plasma processing apparatus comprising:
 a chamber;   a substrate support having a lower electrode and provided in the chamber;   a gas supply configured to supply a processing gas into the chamber;   a plasma generator configured to generate plasma from a gas in the chamber;   a bias power source electrically connected to the lower electrode and configured to periodically generate a pulse of a voltage; and   a controller configured to control the gas supply, the plasma generator, and the bias power source,   wherein the controller is configured to
 (a) control the gas supply and the plasma generator to generate plasma of the processing gas in the chamber, and 
 (b) control the bias power source to periodically apply the pulse to the lower electrode to supply ions from the plasma to a substrate on the substrate support, thereby etching a film of the substrate, and 
   in said (b), the bias power source is controlled to decrease a duty ratio of the pulse at least once such that the duty ratio of the pulse has a tendency to decrease according to progress of the etching of the film.   
     
     
         9 . The plasma processing apparatus to  claim 8 , wherein the pulse is a pulse of a negative voltage or a pulse of a negative direct-current voltage