Patent ID: 7413673

Claim:
A method for performing an inductively coupled plasma etching process, the process being performed in a chamber for etching a wafer, the chamber including a window on a top opening, the window having an outer surface and an inner surface that is exposed to an inner region of the chamber, a coil is positioned over the outer surface of the window and a metal shield is defined over the outer surface of the window, the metal shield being positioned in a spaced apart relationship between the coil and the outer surface of the window, the method comprising: connecting a tuning capacitor to the coil; determining a location of a node on the coil, the node corresponding to a node of a standing radio frequency wave existing on the coil; electrically connecting the coil to the metal shield at a connection location substantially close to the location of the node so as to make the timing capacitor resonant with the standing radio frequency wave existing on the coil; adjusting the tuning capacitor to obtain a required voltage on the metal shield, the required voltage being appropriate for an etching process; and performing the etching process.