Silicon interstitial trapping in polycrystalline silicon films studied by monitoring interstitial reactions with underlying insulating films

Oxidation experiments on structures of polycrystalline silicon on thin oxides indicate that the generated interstitials are partially trapped within the polycrystalline silicon layer and partially escape, diffuse through the underlying thin oxide, and affect pre-grown oxidation induced stacking faults in the silicon. The trapping efficiency of the polycrystalline silicon film has been found to increase with decreasing grain size or increasing him thickness. This indicated that grain boundary traps are primarily responsible for interstitial trapping within the polycrystalline silicon. The larger trapping efficiency of smaller grain size films was attributed to the larger surface of grain boundaries and the larger grain boundary trap concentration in that case. In all cases, polycrystalline silicon films trap more interstitials than crystalline silicon films of the same thickness that were used as a reference in this study. (C) 1996 American Institute of Physics.