OPTICAL PROPERTIES OF PECVD AND UVCVD SiN{sub}x:H ANTIREFLECTION COATINGS FOR SILICON SOLAR CELLS

摘要

A complete study of the optical properties has been achieved for hydrogenated silicon nitride SiN{sub}x:H obtained by either Low Frequency (40kHz) Plasma Enhanced Chemical Vapour Deposition (LF-PECVD) or by another low temperature deposition technique: Ultraviolet photo-assisted CVD (UVCVD). Spectroscopic ellipsometry measurements were carried out on a large number of samples. The results were gathered in a data library in order to compute the wavelength-dependant reflection, absorption and transmission coefficients through the layers. Different optical behaviors were observed according to the deposition technique, with stronger absorption and hence smaller optical gaps for UVCVD films. This is believed to be due to the formation in the SiN{sub}x matrix of amorphous silicon (a-Si) clusters, which seem to be much bigger than those obtained in PECVD layers.