ALUMINUM MEDIATED LOW-TEMPERATURE GROWTH OF CRYSTALLINE SILICON BY PLASMA-ENHANCED CHEMICAL-VAPOR AND SPUTTER-DEPOSITION

The growth of nanocrystalline silicon on an aluminum underlayer of 4-3 2 nm thickness on silica substrates by plasma-enhanced chemical vapor deposition (PECVD) or sputter deposition is observed at standard condi tions for the preparation of device quality hydrogenated amorphous sil icon (substrate temperature of 500 K, deposition rate of 0.5 mu m/h). The crystallite size determined by wide angle x-ray scattering ranges from 10 to 30 nm, and the crystallite fraction reaches 25%. The effici ency of aluminum mediated crystallization is about one order of magnit ude higher for PECVD films than for sputtered films. Variations of the incident angle of the x rays show that the formation of silicon cryst allites takes place at the Al/Si interface. Diffusion of Al into the s ilicon is enhanced for the PECVD films, whereas it plays a comparative ly minor role for sputter deposition. The effect of the aluminum media ted crystallite growth is related to the existence of a metastable alu minum silicide and diffusion processes. (C) 1998 American Institute of Physics.