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Effect of RF or VHF Plasma on Nanocrystalline Silicon Thin Film Structure: Insight from OES and Langmuir Probe Measurements

Published online by Cambridge University Press:  07 August 2013

Lala Zhu ,
Ujjwal K Das ,
Steven S Hegedus  and
Robert W Birkmire
Lala Zhu
Affiliation:
Institute of Energy Conversion, University of Delaware, Newark, Delaware, USA 19716; Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA 19716.
Ujjwal K Das
Affiliation:
Institute of Energy Conversion, University of Delaware, Newark, Delaware, USA 19716;
Steven S Hegedus
Affiliation:
Institute of Energy Conversion, University of Delaware, Newark, Delaware, USA 19716;
Robert W Birkmire
Affiliation:
Institute of Energy Conversion, University of Delaware, Newark, Delaware, USA 19716; Department of Physics and Astronomy, University of Delaware, Newark, Delaware, USA 19716.
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Abstract

Optical emission spectroscopy (OES) and Langmuir Probe were used to characterize RF and VHF plasma properties under conditions leading to nanocrystalline silicon film deposition. Films deposited by RF plasma at low pressure (3 Torr), even with high crystalline volume fraction, show weak X-ray diffraction signals, suggesting small grain size, while RF films at higher pressure (8 Torr) and VHF films at both high and low pressure have larger grain sizes. The preferential growth orientation is controlled by the H2/SiH4 ratio with RF plasma, while the film deposited by VHF shows primarily (220) orientation independent of H-dilution ratio. Langmuir Probe measurements indicate that the high energy electron population is reduced by increasing pressure from 3 Torr to 8 Torr in RF plasma. Compared with RF plasma, the VHF plasma shows higher electron density and sheath potential, but lower average electron energy, which may be responsible for the larger grain size and crystal orientation. The growth rate and crystalline volume fraction of the film is correlated with OES intensity ratio of SiH* and Hα/SiH* for both RF and VHF plasmas.

Keywords

plasma-enhanced CVD (PECVD) (deposition)thin filmSi
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1536: Symposium A – Film Silicon Science and Technology , 2013 , pp. 161 - 166
Copyright
Copyright © Materials Research Society 2013 

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References

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