Current-induced recrystallization of polycrystalline silicon nano thin films deposited at different temperatures and its influences on piezoresistive sensitivity and temperature coefficients

To improve the performance and yield of piezoresistive sensors based on polycrystalline silicon nano thin films (PNTFs), the 80 nm-thick PNTFs were deposited on silicon (1 1 1) substrates by LPCVD at different temperatures and fabricated into cantilever beams. The electrical trimming characteristics and the dependences of gauge factor, temperature coefficient of resistance (TCR) and temperature coefficient of gauge factor (TCGF) on resistor trim with different deposition temperatures were measured. Based on the interstitial-vacancy model, the electrical trimming is explained as the mobility increase caused by current-induced recrystallization of grain boundaries. The conclusions indicate that the changes in gauge factor, TCR and TCGF with resistor trim are due to the grain boundary state variation (including scattering center, grain boundary width, tunneling current, localized and extended state conductions). And the electrical trimming method is testified to be applicable for the resistor trimming of PNTF-based sensors after packaging.