Substrate temperature dependence of homoepitaxial growth of Si using mass selected ion beam deposition

Abstract

Homoepitaxy of silicon at low temperature has been achieved using low-energy mass selected silicon ion beams. Reflection high-energy electron diffraction and Rutherford backscattering spectrometry have been utilized to assess the quality of silicon films deposited from 15 eV 28Si+ beams in the temperature range of 50–350 °C. Auger electron spectroscopy was used to monitor the contaminant levels on the surfaces. The films deposited at 350 °C are epitaxial and of a quality near that of the original substrate. The growth rate at 350 °C is ≊200 times faster than that for solid phase epitaxy. At 50 and 200 °C layer-by-layer epitaxial growth was inhibited and evidence for formation of three-dimensional islands in the early stage of growth followed by transition to an amorphous phase was observed. The transition to an amorphous phase occurred at lower film thickness (smaller ion dose) for lower temperatures. It is shown that small amounts of N+2 impurity in the 28Si+ beam, sufficient to add 1.4 at. % N to the silicon film, result in amorphous films, even at the highest temperature used, 350 °C. The effects of substrate temperature, contamination, and surface damage on the growth mechanism are discussed.