Multiple frequency pulsing of multiple coil source to control plasma ion density radial distribution

摘要

A method is provided for processing a workpiece supported on a support surface in a chamber of a plasma reactor. A process gas is introduced into the chamber and a plasma is generated with pulse-modulated RF power. The method comprises successively repeating the following cycle: (a) concentrating the plasma in the chamber in a center-high plasma ion distribution for a first on-time duration; (b) permitting plasma to drift during a first off-time duration away from the center-high plasma ion distribution; (c) concentrating the plasma in the chamber in an edge-high plasma ion distribution for a second on-time duration; and (d) permitting plasma to drift during a second off-time duration away from the edge-high plasma ion distribution. The method further comprises adjusting a plasma process rate near a center of the workpiece by adjusting a duty cycle of the first on-time and first off-time. The method also comprises adjusting a plasma process rate near a periphery of the workpiece by adjusting a duty cycle of the second on-time and second off-time.