Preparation of Nanocrystalline Silicon by Pulsed Plasma Processing

Abstract

ABSTRACTWe have proposed digital plasma processing for the fabrication of silicon quantum dots with grain size less than l0nm. By using the pulsed gas supply of SiH4 and H2 in the very-high frequency (VHF) plasma, we have clarified the role of atomic hydrogen in the nucleation, crystallization of nanocrystalline Si (nc-Si) as well as in the selective etching of amorphous Si to nc-Si. Recently, we have prepared nc-Si by employing an ultra-high-vacuum (UHV) chamber equipped with VHF plasma cells of SiH4 and H2. Flux rate of Si cluster depends significantly on the pressure of the plasma cell and VHF power. Spherical shaped nc-Si clusters less than 6nm in diameter have been observed by transmission electron microscopy (TEM). Infrared absorption measurements have clarified that the surface of nc-Si is covered by hydrogen. In an attempt to control the position of nuclei, we have prepared nc-Si on SiO2 with micro trenches, 40nm wide and 20nm deep, fabricated by electron beam exposure and electron cyclotron resonance (ECR) etching. It has been revealed by TEM observation that nc-Si are formed preferentially along micro trenches.