Design and manufacturing of a pressure sensor with capacitive readout, CMOS compatible

A capacitive differential pressure sensor, CMOS compatible is designed and realized. The device consists of a variable capacitor realized by silicon bulk and surface micromachining. The upper electrode is a diaphragm which consists in a sandwich of polyimide and metal. The bottom electrode is placed on silicon substrate and is formed by Cr/Au deposition and configuration. The sensor has a 5 mum air gap as a dielectric. It is made from monocrystalline silicon by means of micromachining methods. It has an area of 800x800 mum and a thickness of about 7 m. The sensor can be integrated on one chip with a pre-amplifier circuit. It was designed and simulated using the MEMCAD 4.8 software. In MEMCAD, we designed the 2D and 31) models, according with the technological manufacturing processes. We have simulated the capacitance of the sensor depending on the applied relative pressure. A sensitivity AC/C of about 60% has been shown for a differential pressure of 1 atm. The results of the analysis show that the sensor can be used at relative pressures between 0 and 1,6 atm. The scale of pressures can be enlarged easily by increasing the air gap or by changing the thickness of the polyimide diaphragm. The manufacturing of the device will be briefly described, but the focus lies primarily on the design and simulation of the sensor.