Methods and systems for independent control of radical density, ion density, and ion energy in pulsed plasma semiconductor device fabrication

A method for controlling a plasma in a semiconductor fabrication process, comprising:

• (a) disposing a substrate on a substrate holder within a process module;
• (b) supplying a process gas composition to a plasma generation region overlying the substrate;
• (c) for a first period of time, applying a first radiofrequency power to the process gas composition within the plasma generation region to generate a plasma in exposure to the substrate, the first radiofrequency power corresponding to a high radiofrequency power level, and applying bias voltage at the substrate holder at a first bias voltage setting corresponding to a low bias voltage level that is below a threshold voltage required for removal of a material from the substrate through interaction of ions from the plasma with the material on the substrate;
• (d) for a second period of time, after completion of the first period of time, applying a second radiofrequency power to the process gas composition within the plasma generation region to generate the plasma in exposure to the substrate, wherein the second radiofrequency power is applied instead of the first radiofrequency power, the second radiofrequency power corresponding to a low radiofrequency power level, and applying bias voltage at the substrate holder at a second bias voltage setting corresponding to a high bias voltage level;
• and
• (e) repeating operations (c) and (d) in an alternating and successive manner for an overall period of time necessary to produce a desired effect on the substrate,
• wherein a duration of the first period of time of operation (c) is shorter than a duration of the second period of time of operation (d) such that a time-averaged ion density within the plasma is greater than a time-averaged radical density within the plasma.