Polycrystalline silicon layers with enhanced thermal stability

We report on a new method of external gettering in silicon substrate for semiconductor applications. The proposed method is based on the deposition of a multilayer system formed by introducing a number of thin buried silicon oxide layers into the thick polycrystalline silicon layer deposited on the wafer backside. Oxide films of a few nanometer thicknesses significantly retard both the grain growth and subsequent loss of the gettering capability of the polycrystalline silicon layer during high temperature annealing. The mechanisms of the grain growth and the influence of the embedded oxide layers on the gettering function in the multilayer system are discussed. We used scanning electron microscopy and transmission electron microscopy for the characterization of the multilayer system, and intentional contamination for demonstration of the gettering properties.