PIEZORESISTIVITY EFFECTS IN MOS-FET USEFUL FOR PRESSURE TRANSDUCERS

The piezoresistivity coefficients in p- and n-channel MOS transistors manufactured on silicon wafers cut parallel to the (111) and (100) planes as a function of VD, VG and of the temperature, between -20 and 120 degrees C, have been measured with the particular aim of investigating the possible application of MOS transistors for strain measurements, by comparing the advantages and the disadvantages with bulk and diffused resistors. The characteristics of the MOS devices can be consistently better than the corresponding ones of bulk semiconductor strain gauges, particularly as regards the temperature stability of the resistivity and of the electrical characteristics.