PRESSURE SENSITIVITY IN ANISOTROPICALLY ETCHED THIN-DIAPHRAGM PRESSURE SENSORS

In this paper the differential equations governing thin, square-diaphragm silicon pressure sensors are developed and solved using finite-difference numerical methods. Diaphragm deflection and stress patterns are presented in a normalized form applicable to diaphragms of arbitrary thickness and size. For 1-mm2 10-jum-thick diaphragms in <100> silicon, the calculated pressure sensitivity of full-bridge piezoresistive sensors is about 68 mV per volt supply per mmHg, which agrees well with experimental data. Variations in the pressure sensitivity of piezoresistive and capacitive structures due to process-induced variations in diaphragm thickness, size, taper, alignment, and resistor size are evaluated. Sensitivity is influenced most strongly by diaphragm thickness, with alignment an important secondary consideration in resistive devices. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.