Patent ID: 8158016

Claim:
A method of operating a radiofrequency ion source that includes a discharge chamber having a discharge space therein, an electromagnet disposed at a first end of the discharge space, and a first pole piece formed from a magnetically permeable material disposed proximate the electromagnet, the method comprising: generating a plasma with a plasma density distribution from a working gas in the discharge space of the discharge chamber; applying a current to the electromagnet to generate a magnetic field; magnetizing the first pole piece so as to change the plasma density distribution in the discharge space of the discharge chamber; extracting an ion beam from the plasma with at least one electrode disposed at a second end of the discharge space; determining an actual distribution profile of a density of the ion beam proximate to a wafer processing location; comparing the actual distribution profile of the ion beam density with a desired distribution profile for the ion beam density; and based upon the comparison, adjusting the current applied to the electromagnet to alter the magnetization of the first pole piece and further change the plasma density distribution in the discharge space of the discharge chamber.