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Regrowth Rates of Amorphous Layers in Silicon-on-Sapphire Films

Published online by Cambridge University Press:  26 February 2011

P. J. Timans
Affiliation:
Microelectronics Research Laboratory, Cambridge University, Cambridge Science Park, Milton Road, Cambridge CB4 4FW, U.K.
R. A. McMahon
Affiliation:
Microelectronics Research Laboratory, Cambridge University, Cambridge Science Park, Milton Road, Cambridge CB4 4FW, U.K.
H. Ahmed
Affiliation:
Microelectronics Research Laboratory, Cambridge University, Cambridge Science Park, Milton Road, Cambridge CB4 4FW, U.K.
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Abstract

The rate and direction of regrowth of amorphous layers, created by self-implantation, in silicon-on-sapphire (SOS) have been studied using time resolved reflectivity (TRR) experiments performed simultaneously at two wavelengths. Regrowth of an amorphous layer towards the surface was observed in specimens implanted with 3.1015Si+/cm2 at 50keV and regrowth of a buried amorphous layer, from a surface seed towards the sapphire, was observed in specimens implanted with 1.1015Si+/cm2 at 175keV. Rapid isothermal heating to regrow the layers was performed in an electron beam annealing system. The combination of 514.5nm and 632.8nm wavelengths was found to be particularly useful for TRR studies since the high absorption in amorphous silicon, at the shorter wavelength, means that the TRR trace is not complicated by reflection from the silicon-sapphire interface until regrowth is nearly complete. The dual wavelength method removes ambiguity about the position of the amorphous to crystalline interface and the direction of regrowth. The temperature dependence of the refractive index of silicon leads to large changes in the reflectivity of SOS films as they are heated. The combination of regrowth rate observations and reflectivity measurements during heating has been used to characterize the isothermal heating cycle, avoiding the difficulties of using pyrometers operating at the useful near infra-red wavelengths, where sapphire is transparent.

Type
Research Article
Copyright
Copyright © Materials Research Society 1986

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