Influence of impurity distribution on thermal coefficients of resistivity and piezoresistivity of diffused layers in silicon

This work presents a numerical investigation of impurity distribution changes caused by technological parameters variations and their influence on thermal sensitivity of piezoresistive pressure sensors. It is shown that the ratio of thermal coefficients of resistivity and piezoresistivity for a sensor may be optimized by a proper choice of process parameters. In this way the conditions are provided for simple passive temperature compensation. The goal of this work was to give a simplified and quick procedure for numerical prediction of the impurity profiles corresponding to optimum values of thermal coefficients of silicon pressure sensors. Contrary to the generally accepted theory, it was shown that the thermal coefficients depend not only on the impurity concentration on the surface, but on their distribution near the surface as well, which can be used in practical optimization of these coefficients.