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Investigation of the Surface Morphology of a-Si:H by Atomic Force Microscopy and In-Situ Ellipsometry

Published online by Cambridge University Press:  15 February 2011

H. N. Wanka ,
A. Hierzenberger  and
M. B. Schubert
H. N. Wanka
Affiliation:
Univ. Stuttgart, Inst. f. Physikalische Elektronik, Pfaffenwaldring 47, D-70569 Stuttgart, Germany
A. Hierzenberger
Affiliation:
Univ. Stuttgart, Inst. f. Physikalische Elektronik, Pfaffenwaldring 47, D-70569 Stuttgart, Germany
M. B. Schubert
Affiliation:
Univ. Stuttgart, Inst. f. Physikalische Elektronik, Pfaffenwaldring 47, D-70569 Stuttgart, Germany
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Abstract

Combining real-time ellipsometry and atomic force microscopy (AFM) the growth of hydrogenated amorphous silicon (a-Si:H), deposited on crystalline silicon wafers with a native oxide layer on top and on fused silica from a dc glow discharge, has been studied from initial nucleation to the final morphology. By in-situ ellipsometry we detected the evolution of morphology changes. The surface structure has been determined by AFM in the nucleation phase and in the subsequent growth stage. During nucleation on crystalline silicon only few (about 40 per 1μm) flat islands of a-Si:H (up to 4 nm high and up to 50 nm in diameter) grow with a strongly enhanced rate compared to bulk deposition. Once the crystalline surface has completely been covered by a-Si:H, the fast deposition of these islands stops and further surface structures, comparable with the initial ones, start to grow gradually until a homogeneous final roughness up to 5nm high is formed. Nucleation of a-Si:H on fused silica yields densely distributed nuclei (up to 1.5 nm high and up to 25 nm in diameter), indicating a shorter surface diffusion length on this substrate compared to the growth on silicon wafers. The ongoing film deposition, however, finally results in a morphology comparable to the one of a-Si:H grown on crystalline silicon. Using hydrogen dilution we found that the final roughness is affected by the dilution ratio; furthermore infrared spectroscopy reveals the surface structure to be correlated with the hydrogen content of the a-Si:H films.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 377: Symposium A – Amorphous Silicon Technology 1995 , 1995 , 263
Copyright
Copyright © Materials Research Society 1995

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References

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