Precise control of ion energy distributions by high frequency pulsed voltage waveforms in inductively coupled plasmas

The utilization of inductively coupled plasmas is becoming increasingly prevalent in a diverse range of technological applications, where precise control of the ion energy distribution (IED) is essential. In many instances, narrow single-peak IEDs at controllable energies are necessary, for instance, to enhance selectivity in plasma etching, which cannot be achieved in classical plasma etching systems with radio frequency waveform biasing. In this work, we employ a theoretical model that allows for rapid calculation of the IED to design the scheme of high frequency pulsed voltage waveforms for precise ion energy control in inductively coupled plasmas. The ions undergo multiple cycles as they transit through the sheath, and the ions respond to the average bias sheath potential. The use of a pulsed voltage bias power supply with a frequency of 10 MHz in an inductively coupled plasma etching system yielded mono-energetic ions with narrow single-peak IEDs (minimum ion energy spread of 9 eV) in the experiment. Furthermore, the precise determination of the physical sputter etch threshold of the substrate material indicates that precise control of ion energy is possible through the use of the high frequency pulsed voltage waveforms.