Temperature characteristics of polysilicon piezoresistive nanofilm depending on film structure

The influence of film structure on temperature characteristics of polysilicon nanofilms (PSNFs) was reported in this paper. Samples were deposited by LPCVD with different film thickness and deposition temperature. The microstructure of films was characterized by SEM, TEM and XRD. By measuring the resistivity and the gauge factor of samples at different temperatures, temperature coefficients of the resistance and the gauge factor (TCR and TCGF) were investigated. Based on the analysis of tunneling piezoresistive effect, the results indicated that PSNFs of ultrahigh doping concentration (around 3times10²⁰ cm^-3) have better piezoresistive temperature characteristics than single crystal silicon. By controlling the process parameters like deposition temperature and film thickness, film structure was optimized to obtain a very low resistance temperature coefficient (about plusmn10^-4/degC). Moreover TCGF was negative and almost not affected by deposition temperature and film thickness. These conclusions are useful for temperature compensation of polysilicon pressure sensors.