Effect of Ion Energy on Microcrystalline Silicon Material and Devices: A Study Using Tailored Voltage Waveforms

Abstract

The use of tailored voltage waveforms to excite a plasma has been shown to be an effective technique to decouple maximum ion energy from the ion flux on the electrode. We use it here as a way to scan through the maximum ion energy in order to study this quantity's role in the growth of μc-Si:H. We find that at critical energies (30 and 70 eV), a stepwise increase in the a-Si:H/μc-Si:H transition thickness is observed, together with change in the surface morphology. These thresholds correspond to SiH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> - and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -induced displacement energies, respectively. A model is proposed to account for the impact of these ions on the morphology of μc-Si:H growth and is confirmed by comparison with epitaxial growth on a crystalline wafer.