Etching method and apparatus

Abstract

An etching method capable of controlling the film thickness of a hard mask layer uniformly is provided. A plasma etching is performed on a native oxide film by using an etching gas containing, for example, CF 4 and Ar while a thickness of a silicon nitride film is being monitored and the etching is finished when the thickness of the silicon nitride film reaches a predetermined value. Then, a plasma etching is performed on a silicon substrate by employing an etching gas containing, for example, Cl 2 , HBr and Ar and using the silicon nitride film as a mask while a depth of a trench is being monitored and the etching is finished when the depth of the trench reaches a specified value.

1 . An etching apparatus for performing an etching on a substrate including a mask layer having a pattern; a first layer formed in a groove portion of the pattern; and a second layer formed beneath the mask layer and the first layer, comprising: 
 a plasma source for generating a plasma;    a processing chamber for performing the etching on the substrate by using the plasma;    a substrate supporting table, installed in the processing chamber, for mounting the substrate thereon;    a gas exhaust unit for depressurizing the processing chamber;    a gas supply unit for supplying a gas into the processing chamber;    a film thickness monitoring unit for monitoring a thickness of the mask layer; and    a controller for controlling an etching process based on film thickness information provided from the film thickness monitoring unit.    
   
   
       2 . The etching apparatus of  claim 1 , wherein the film thickness monitoring unit includes: 
 a light source for irradiating a light toward the substrate;    a spectrometer unit for dispersing a reflected light from the substrate into its spectrum;    a light detection unit for detecting the spectrum; and    an operation unit for processing detection results from the light detection unit based on a calibration curve obtained in advance,    wherein the film thickness monitoring unit is configured to comprise the steps of irradiating the light to the mask layer; detecting a reflected light from a surface of the mask layer and a reflected light from an interface between the mask layer and the second layer; calculating a spectral reflectance; and measuring the thickness of the mask layer based on the calibration curve obtained in advance by employing a curve fitting method.    
   
   
       3 . The etching apparatus of  claim 1 , wherein the controller terminates an etching of the first layer and starts an etching of the second layer when the thickness of the mask layer reaches a specified value based on the film thickness information provided from the film thickness monitoring unit.  
   
   
       4 . The etching apparatus of  claim 1 , wherein the mask layer is a silicon nitride film.  
   
   
       5 . The etching apparatus of  claim 1 , wherein the second layer is a silicon layer and the first layer is a native oxide film formed on a surface of the silicon layer in the groove portion.  
   
   
       6 . The etching apparatus of  claim 5 , wherein after etching the native oxide film, an etching of the silicon layer is performed by using the mask layer as a mask while an etched depth of the silicon layer is being monitored and finished when the etched depth reaches a specified value.  
   
   
       7 . The etching apparatus of  claim 6 , which is applied to a trench etching in shallow trench isolation.