| CPC H01J 37/32009 (2013.01) [H01J 37/32146 (2013.01); H01J 37/32174 (2013.01); H01J 37/32706 (2013.01); H01J 37/32935 (2013.01); H01J 37/3299 (2013.01)] | 9 Claims |

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1. A method, comprising:
applying a modified periodic voltage function to an electrode of a substrate support of a process chamber to set a wafer voltage for a wafer, wherein the applying the modified periodic voltage function comprises:
(a) delivering a first plurality of voltage pulses that are delivered during a first period wherein each pulse of the first plurality of voltage pulses comprises a first negative voltage step;
(b) delivering a second plurality of voltage pulses that are delivered during a second period wherein each pulse of the second plurality of voltage pulses comprises a second negative voltage step wherein the first negative voltage step is different than the second negative voltage step; and
repeating (a) and (b) a plurality of times to generate an ion energy distribution function that has a plurality of energy peaks in a plasma formed in the process chamber; and
wherein each pulse comprises a portion between the negative voltage step and a positive voltage step of a next pulse.
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