MEMS-based capacitive pressure sensors with pre-stressed sensing diaphragms

This paper presents a MEMS-based capacitive pressure sensor with pre-stressed sensing diaphragms for achieving a linear response with applied pressure. The sensor is designed to work in touch-mode by using sensing pressure diaphragms with compressive residual stress on top of insulated counter electrodes. FEM (Finite Element Method) calculation shows that a sensing diaphragm with residual stress can provide superior linear response than a stress-free diaphragm. The device is fabricated on a Si substrate using surface micromachining. LPCVD (low pressure chemical vapor deposition) oxide is used to seal the pressure cavity and to form the dielectric insulation layer. The experimental results show that the MEMS pressure sensor responds linearly in the pressure range of 16-215 psi with a sensitivity of 0.092 pF/psi and full scale nonlinearity of 3.3% without compensation.