Proceedings of the Tenth European Conference on Chemical Vapour Deposition

J. Phys. IV France 05 (1995) C5-1165-C5-1172
DOI: 10.1051/jphyscol:19955138

Low-Temperature Epitaxial Growth Mechanism of Si_1-xGe_x Films in the Silane and Germane Reactions

J. Murota¹, Y. Takasawa², H. Fujimoto³, K. Goto⁴, T. Matsuura¹ and Y. Sawada<sup>1

1</sup>  Laboratory for Electronic Intelligent Systems, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-77, Japan
²  On leave from Kokusai Electric Co., Ltd., Toyama Works, 2-1 Yasuuchi, Yatsuomachi, Neigun, Toyama 939-23, Japan
³  On leave from Miyagi OKI Electric Co., Ltd., 1 Okinodaira, Ohiramura, Kurokawagun, Miyagi 981-36, Japan
⁴  DC Research Fellow of the Japan Society for the Promotion of Science

Abstract
Low-temperature epitaxial growth of undoped and doped Si_1-xGe_x films on the Si(100) surface at 550°C was investigated under the cleanest possible reaction environment of SiH₄, GeH₄ and H₂ with the PH₃ or B₂H₆ addition using an ultraclean hot-wall low-pressure chemical vapour deposition (LPCVD) system. The SiH₄ and GeH₄ reaction rates are expressed by the Langmuir-type rate equation, assuming that one SiH₄ or GeH₄ molecule is adsorbed at a single adsorption site, according to the Langmuir's adsorption isotherm, and decomposes there. It is found that the SiH₄ and GeH₄ adsorption rate constants become larger at the bond site of the Si-Ge pair than those at the others, while the SiH₄ surface reaction rate constant becomes the largest at the bond site of the Ge-Ge pair. With the PH₃ and B₂H₆ addition, the incorporation rate of P and B increased proportionally and was higher with a higher Ge fraction x in the film. This was explained by the increase of the free site density and the difference of free site materials according to the Langmuir-type rate equation. In the case of P doping, it is found that electrically inactive P is formed with high Ge fractions.

© EDP Sciences 1995