Low temperature diffusion effects on microstructural changes in thick gold films on silicon

Abstract

The formation of a silicon oxide layer and the microstructural changes in thick sputtered deposited gold films on Si(111) substrates were studied by scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods. Redistribution of silicon, gold and oxygen was analysed by Auger electron spectroscopy and secondary-ion mass spectrometry sputter profiling and electron probe microanalysis. It was found that structures formed during low temperature annealing in air up to 250°C consist of several separated zones. In the outer structure zone a thick porous silicon oxide layer with a needle-like structure is honeycombed with columnar gold grains, thus forming a mixed zone. The thickness of the gold and silicon oxide zone increases with increasing temperature until the substantial gold grain growth at the Au Si interface zone impedes the release of silicon atoms and their further outdiffusion and oxidation.