Control of Plasma Uniformity Using Phase Difference in a VHF Plasma Process Chamber

Very high frequency (VHF) capacitively coupled plasma sources are widely used for semiconductor manufacturing processes. Uniform plasma can be difficult to achieve at VHF for different load conditions (pressure, power, gas mixture electronegativity, etc.). This paper discusses how voltage phase difference between top and bottom electrodes can be used to control plasma uniformity above the wafer.