The nucleation and growth of glow-discharge hydrogenated amorphous silicon

Abstract

We present detailed analysis of in situ ellipsometry measurements taken during the deposition of hydrogenated amorphous silicon (a-Si:H) on crystalline silicon substrates in a conventional rf glow-discharge apparatus. This analysis concentrates on the initial growth data (<100 Å in thickness) which exhibit measurable deviation from a uniform growth model. Taking into account a surface roughness layer estimated from spectroscopic ellipsometry measurements, the deviation is found to be consistent with a nucleation process whereby the a-Si:H coalesces to bulk density at a thickness of about 55 Å. By stopping the glow discharge and restarting it again without changing the deposition parameters, the regrowth process and the nature of the regrowth interface have been studied. We have observed extremes in behavior from renucleation on a scale of 35 Å to the formation of an 80-Å-thick structurally defective layer at the regrowth interface. Such results provide a direct measure of the extent of structurally defective layers at amorphous semiconductor interfaces.