Method of etching and etching apparatus

Abstract

Silicon oxide film having, as a sublayer, a silicon nitride film layer serving as a protective film layer for gate formed on silicon substrate is etched by introducing a processing gas including a gaseous mixture containing at least C 4 F 6 , Ar, O 2 and N 2 into an airtight processing chamber and carrying out a plasma treatment in a self-alignment contact process, thereby forming contact hole. For the processing gas, e.g., the ratio of N 2 gas flow rate to C 4 F 6 gas flow rate ranges from 25/8 to 85/8, the ratio of O 2 and N 2 gas flow rate to C 4 F 6 gas flow rate ranges from 15/4 to 45/4 and the ratio of N 2 gas flow rate to O 2 gas flow rate ranges from 5 to 17. Accordingly, stable contact holes of high aspect ratio exhibiting desirable control characteristics is formed while minimizing etching the silicon nitride film, a protective film layer for gate.

1 . An etching method, in which a processing gas is fed into an airtight processing chamber to generate a plasma therein and a silicon-containing oxide film formed on an object to be processed disposed in the processing chamber is selectively etched against a silicon nitride film, wherein the processing gas is a gaseous mixture including at least a fluorocarbon-based gas, a first deposit removing gas and a second deposit removing gas having a weaker deposit removing capability than the first deposit removing gas.  
   
   
       2 . The etching method of  claim 1 , wherein an etching selectivity of the silicon-containing oxide film to the silicon nitride film is set to a predetermined value by a ratio of a total flow rate of the first and the second deposit removing gas to a flow rate of the fluorocarbon-based gas, and a ratio of a flow rate of the second deposit removing gas to the flow rate of the fluorocarbon-based gas.  
   
   
       3 . The etching method of  claim 1 , wherein the silicon-containing oxide film is a silicon oxide film.  
   
   
       4 . The etching method of  claim 1 , wherein the fluorocarbon-based gas is a C 4 F 6  gas, the first deposit removing gas is an oxygen gas and the second deposit removing gas is a nitrogen gas.  
   
   
       5 . The etching method of  claim 4 , wherein, in the processing gas, a ratio of a flow rate of the N 2  gas to a flow rate of the C 4 F 6  gas is greater than or equal to about 25/8 and less than or equal to about 85/8, and a ratio of a total flow rate of O 2  and N 2  to the flow rate of the C 4 F 6  gas is greater than or equal to about 15/4 and less than or equal to about 45/4.  
   
   
       6 . The etching method of  claim 4 , wherein, in the processing gas, a ratio of a flow rate of the N 2  gas to a flow rate of the C 4 F 6  gas is greater than or equal to about 25/8 and less than or equal to about 85/8, and a ratio of the flow rate of the N 2  gas to a flow rate of the O 2  gas is greater than or equal to about 5 and less than or equal to about 17.  
   
   
       7 . The etching method of  claim 1 , wherein the processing gas includes an inert gas.  
   
   
       8 . The etching method of  claim 1 , wherein an upper and a lower electrode are installed opposite to face each other in the processing chamber, a first high frequency power is applied to the upper electrode and a second high frequency power is applied to the lower electrode, a frequency of the second high frequency power is lower than that of the first high frequency power.  
   
   
       9 . The etching method of  claim 8 , wherein the frequency of the first high frequency power is about 60 MHz and that of the second high frequency power is about 2 MHz.  
   
   
       10 . The etching method of  claim 3 , wherein the silicon nitride film exists under the silicon oxide film.  
   
   
       11 . The etching method of  claim 10 , wherein the silicon oxide film is etched in a self-alignment contact process.  
   
   
       12 . An etching apparatus, in which a processing gas is fed into an airtight processing chamber to generate a plasma therein and a silicon-containing oxide film formed on an object to be processed disposed in the processing chamber is selectively etched against a silicon nitride film, wherein the processing gas is a gaseous mixture including at least a fluorocarbon-based gas, a first deposit removing gas and a second deposit removing gas having a weaker deposit removing capability than the first deposit removing gas.  
   
   
       13 . The etching apparatus of  claim 12 , wherein an etching selectivity of the silicon-containing oxide film against the silicon nitride film is set by a ratio of a total flow rate of the first and the second deposit removing gas to a flow rate of the fluorocarbon-based gas and a ratio of a flow rate of the second deposit removing gas to the flow rate of the fluorocarbon-based gas.  
   
   
       14 . The etching apparatus of  claim 12 , wherein the silicon-containing oxide film is a silicon oxide film.  
   
   
       15 . The etching apparatus of  claim 12 , wherein the fluorocarbon-based gas is a C 4 F 6  gas, the first deposit removing gas is an oxygen gas, and the second deposit removing gas is a nitrogen gas.  
   
   
       16 . The etching apparatus of  claim 15 , wherein, in the processing gas, a ratio of a flow rate of the N 2  gas to a flow rate of the C 4 F 6  gas is greater than or equal to about 25/8 and is less than or equal to about 85/8, and a ratio of a total flow rate of O 2  and N 2  to the flow rate of the C 4 F 6  gas is greater than or equal to about 15/4 and is less than or equal to about 45/4.  
   
   
       17 . The etching apparatus of  claim 15 , wherein, in the processing gas, a ratio of a flow rate of the N 2  gas to a flow rate of the C 4 F 6  gas is greater than or equal to about 25/8 and less than or equal to about 85/8, and a ratio of the flow rate of the N 2  gas to a flow rate of the O 2  gas is greater than or equal to about 5 and less than or equal to about 17.  
   
   
       18 . The etching apparatus of  claim 12 , wherein the processing gas includes an inert gas.  
   
   
       19 . The etching apparatus of  claim 12 , wherein an upper and a lower electrodes are installed opposite to face each other in the processing chamber, a first high frequency power is applied to the upper electrode, and a second high frequency power is applied to the lower electrode, a frequency of the second high frequency being lower than that of the first high frequency power.  
   
   
       20 . The etching apparatus of  claim 19 , wherein the frequency of the first high frequency power is about 60 MHz, and that of the second high frequency power is about 2 MHz.  
   
   
       21 . The etching apparatus of  claim 14 , wherein the silicon nitride film exists under the silicon oxide film.  
   
   
       22 . The etching apparatus of  claim 21 , wherein the silicon oxide film is etched in a self-alignment contact process.