Piezoresistive properties of polycrystalline and crystalline silicon films

Abstract The piezoresistive properties of thin polycrystalline and crystalline boron-doped silicon films on thermally oxidized silicon substrates are reported, based on their calculated and measured gauge factors. A simple theoretical model for calculating the longitudinal and transverse gauge factors, including grain size, crystallite orientation and doping dependence, is described. Boron doping concentrations in the range 5 × 10 18 cm −3 to 1 × 10 20 cm −3 have been investigated. Predictions of gauge factors using our model give good agreement with experimental results. Maximum gauge factors of K 1 ≅ 37 and K t ≅ −9 for polycrystalline silicon with grain sizes of about 120 nm were obtained at doping concentrations of about 1 × 10 19 cm −3 . In the case of completely crystalline silicon films, the advantages of SOI technology are combined with excellent piezoresistive properties comparable to those of usual piezoresistors in monocrystalline silicon devices.