A New Silicon Diaphragm Pressure Sensor and its Stress Analysis

A conventional flat silicon diaphragm does not perform well in a low pressure range sensor that requires high output and high accuracy because the large deflection of diaphragm causes severe nonlinearity when the diaphragm thickness is small for high output. This phenominon is known as the balloon effect. In order to solve this problem, an improved structure with two bulk masses on the back of a square or rectangular diaphragm has been proposed for silicon pressure sensors. The diffused piezoresistive gauges are formed on the diaphragm between the two bulk masses and between either bulk mass and diaphragm edge, where the stress is concentrated. The two dimensional stress analysis of this structure using finite element method are given, The results are helpful for the optimization design. The experimental results show that the sensitivity of this kind of sensor is about two times or more as large as that of conventional square diaphragm pressure sensor with same diaphragm thickness and size, which agrees well with the analytical results.