THERMAL DRIFTS OF MICROELECTRONIC CAPACIT IVE PRESSURE SENSOR

The thermal drifts of microelectronic capacitive pressure sensor have been analysed by finite-element method. Various boundary conditions re presenting a wide gamut of support of sensor have been considered: sen sor with free base, sensor with fixed base and sensor attached to a su pport of alumina. For every case, the thermal response of sensor have been determined as a function of sensor dimensions in order to push fa r the buckling temperature and hence reduce the thermal sensitivity. F or some sensors very sensitive to pressure, this temperature is small and the thermal drifts are important. A sensor with fixed base having a diaphragm of 1000 mu m of radius and 12 mu m of thickness and having a 3.5 mu m of plate separation presents a thermal sensitivity of -200 Pa degrees C-1 above 80 degrees C. A sensor attached to a support of alumina, having a more wide diaphragm (1800 mu m of radius) presents a thermal sensitivity of 3.1 Pa C-o(-1) below -100 degrees C.