Structural study of initial layer for μc-Si:H growth using real time in situ spectroscopic ellipsometry and infrared spectroscopy

Real time observations by spectroscopic ellipsometry (SE) and infrared attenuated total reflection spectroscopy (ATR) have been performed to characterize initial layers from which mu c-Si:H nucleates in rf plasma-enhanced chemical vapor deposition. The SE analysis showed an enhanced surface smoothening of a-Si:H layers with increasing hydrogen dilution ratio, R (= [H](2)/[SiH4]), owing to surface diffusion of precursors. No change was found for the absorbance intensities of SiH and SiH2 bonds in the a-Si:H bulk layers with variation of R, while mu c-Si:H formation reduces the incorporation of SiH bonds. In contrast, sub-surface analyses performed by Ar plasma treatment of the deposited a-Si:H layers showed larger sub-surface hydrogen contents in the a-Si:H incubation layers deposited at larger R than those in a-Si:H layers deposited without hydrogen dilution. We suggest that the a-Si:H network formation process in the sub-surface differs in a-Si:H deposition at larger R compared with the smaller R case and this causes the mu c-Si:H nucleation. (C) 2000 Elsevier Science B.V. All rights reserved.