The influence of doping concentration on piezoresistive temperature characteristics of polysilicon nanofilms

Abstract

Compared with ordinary polysilicon films and monocrystalline silicon, heavy doped polysilicon nanofilms have better piezoresistive properties and better temperature characteristics. Therefore, pressure sensors made of polysilicon nanofilms will have many corresponding advantages, including high sensitivity and complete self-compensation of temperature coefficients. In this paper, the influence of doping concentration on temperature coefficient of resistance (TCR) and temperature coefficient of gauge factor (TCGF) is deeply studied to optimize doping concentration in order to make temperature coefficients lowest. TCR and TCGF of samples with doping concentration of 4.1×10¹⁹cm^-3, 1.0×10²⁰cm^-3, 2.0×10²⁰cm^-3, 4.1×10²⁰cm^-3, 7.1×10²⁰cm^-3 are tested at temperature range 23°C to 270°C, respectively, and the microstructures of the samples are also observed by the method of scanning electron microscopy (SEM) and transmission electron microscope (TEM). The experimental results have been explained reasonably based on the tunneling piezoresistive theory proposed before. Based on both experimental results and theoretical analyses, to obtain a zero value of TCR and a low value -0.1%/°C of TCGF, the optimal doping concentration of the films of 80nm thickness should be about 3×10²⁰cm^-3.