Abstract
This paper describes an evaluation method for the piezoresistive property of polycrystalline silicon (polysilicon) materials. In this method, the piezoresistive property of polysilicon is evaluated by deriving the upper and lower bounds using the fundamental piezoresistive coefficients of single-crystalline silicon (SCS). For simplification, we made assumptions about polysilicon that the piezoresistive effect in grain boundaries is negligible and the SCS grains are randomly oriented. For establishing this evaluation method, we employed two approximation models on the basis of two extreme assumptions of uniform stress and fractional change in resistivity throughout polysilicon. The piezoresistive properties derived from these approximation models were successfully defined as the upper and lower bounds. The piezoresistive property of polysilicon measured in previous works lay between the upper and lower bounds for high doping levels suitable for sensing applications. This result supports the applicability of this evaluation method for piezoresistive property of polysilicon.
