Voltage Waveform Tailoring in a RF-CCP reactor: Exploration of self-bias, electron density and current waveform

摘要

We have investigated plasma production in a capacitively-coupled RF reactor using non-sinusoidal waveforms. This technique allows control of the energy of ions bombarding a substrate in Plasma Enhanced Chemical Vapour Deposition (PECVD) processes by the Electrical Asymmetry Effect (EAE). We have compared sinusoidal excitation against two asymmetric waveforms (peaks and valleys) with a fundamental frequency 15 MHz. The electron density was measured by hairpin resonator probe and the current an voltage waveforms were determined using a novel derivative probe. We investigated different gases (Ar, H_2, SiH_4 and H_2) over a range of pressures (from 100 mTorr to 1 Torr) and voltage peak-to-peak amplitudes (from 100 V to 400 V). The tailored waveforms were found to produce significantly higher electron densities compared to sinusoidal excitation of the same amplitude and fundamental frequency.