Interaction of metal layers with polycrystalline Si

Solid-phase reactions of metal films deposited on 0.5-μm-thick polycrystalline layers of Si grown by chemical vapor deposition at 640 °C were investigated by MeV 4He backscattering spectrometry, glancing angle x-ray diffraction, and SEM observations. For the metals Al, Ag, and Au, which form simple eutectics, heat treatment at temperatures below the eutectic results in erosion of the poly-Si layer and growth of Si crystallites in the metal film. Crystallite formation is observed at T≳550 °C for Ag, T ≳400 °C for Al, and T ≳200 °C for Au films. For the metals Pd, Ni, and Cr, heat treatment results in silicide formation. The same initial silicides (Pd2Si, Ni2Si, and CrSi2), are formed at similar temperatures on single-crystal substrates.