Patent ID: 7955986
Filing Date: 2011-06-07
Classification: H01J

Abstract:
1. In a plasma reactor chamber for processing a semiconductor workpiece, a method of controlling plasma ion distribution within the chamber relative to a desired distribution, comprising: providing an RF power applicator for said chamber; providing plural separate concentric coils of different diameters overlying said chamber concentric with a cylindrical axis of symmetry of said chamber and lying in respective exclusive planes parallel with a workpiece support plane of said chamber; applying RF plasma source power to said RF power applicator to generate a plasma within said chamber, said plasma having an ambient radial distribution in absence of said magnetic field; changing distribution of said plasma in said chamber from said ambient distribution to a distribution that approximates said desired plasma distribution, by (1) determining a difference between said ambient distribution and said desired distribution, (2) computing a set of D.C. electric currents that, when applied to respective ones of said coils, corrects said difference, and (3) applying respective ones of said set of D.C. currents to respective ones of said coils; wherein said computing comprises: (b) in a computer, searching for a set of respective coil currents in respective ones of said coils that produce, in accordance with said relationship, a composite magnetic pressure from all of said coils corresponding to said difference; wherein said searching comprises computing in said computer a trial composite magnetic pressure for each one of said set of coil currents.