Mechanics of the silica cap during zone melting of Si films

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Abstract
Zone melting recrystallization of polycrystalline silicon films on oxidized wafers, performed using linear strip heaters, is an easy way of obtaining good quality silicon-on-insulator films. After recrystallization, the top silicon surface has undulations which are very detrimental when applications in very-large-scale integration circuits are being considered. In this paper, which is the first quantitative study of this mass transport, the silica viscosity derived from experiments at 1685 K has been estimated at 2–3.4×108 decapoises, and the silicon undulations are found to vary as the inverse of the cap thickness. We therefore demonstrate that the mechanical resistance of the silica cap is the mechanism which limits the silicon mass transport during zone melting, and his cap behavior is in good agreement with the classical properties of silica at 1685 K.

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