Methods for actively controlling RF peak-to-peak voltage in an inductively coupled plasma etching system

Abstract

An inductively coupled plasma etching apparatus includes a chamber and a window for sealing a top opening of the chamber. The window has an inner surface that is exposed to an internal region of the chamber. A metal plate, which acts as a Faraday shield, is disposed above and spaced apart from the window. A coil is disposed above and spaced apart from the metal plate. The coil is conductively connected to the metal plate at a connection location that is configured to generate a peak-to-peak voltage on the metal plate that optimally reduces sputtering of the inner surface of the window while substantially simultaneously preventing deposition of etch byproducts on the inner surface of the window. In another embodiment, the apparatus includes a controller for externally applying a peak-to-peak voltage to the metal plate. The controller includes an oscillation circuit, a matching circuit, an RF generator, and a feedback control for monitoring the applied peak-to-peak voltage. Methods for optimizing operation of an inductively coupled plasma etching apparatus also are described.

What is claimed is:  
     
         1 . A method for optimizing operation of an inductively coupled plasma etching apparatus, comprising: 
 supplying a chamber for etching a wafer;    attaching a window to a top opening of the chamber, the window having an outer surface and an inner surface that is exposed to an inner region of the chamber;    placing a coil over the window;    placing a metal plate over the outer surface of the window, the metal plate being positioned in a spaced apart relationship between the coil and the outer surface of the window;    connecting the metal plate to a connection location on the coil, the connection location being between an input terminal and an output terminal and being optimally selected so as to produce substantially uniform incident ion energy proximate to the inner surface of the window, the substantially uniform incident ion energy being configured to reduce sputtering of the inner surface of the window while substantially simultaneously preventing deposition of etch byproducts on the inner surface of the window.    
     
     
         2 . A method for optimizing operation of an inductively coupled plasma etching apparatus, comprising: 
 supplying a chamber for etching a wafer;    attaching a window to a top opening of the chamber, the window having an outer surface and an inner surface that is exposed to an inner region of the chamber;    placing a coil over the window;    placing a metal plate over the outer surface of the window, the metal plate being positioned in a spaced apart relationship between the coil and the outer surface of the window; and    applying a controlled peak-to-peak voltage to the metal plate so as to produce substantially uniform incident ion energy proximate to the inner surface of the window, the substantially uniform incident ion energy being configured to reduce sputtering of the inner surface of the window while substantially simultaneously preventing deposition of etch byproducts on the inner surface of the window.