Sem Overestimation of the Mean Grain-size of Chemically Etched Polycrystalline Silicon Films

Scanning electron microscopy (SEM) has been employed to investigate the mean grain sizes of P-doped polycrystalline silicon films produced by low-pressure chemical vapour deposition (LPCVD). A chemical etching standard procedure has been used to obtain SEM high contrast between polycrystalline grains and their boundaries. It has been found that this method, often used in materials laboratories, may cause a large overestimation of the layer's mean grain size. A simple model explaining the obtained results has been proposed.