Research Of Capacitive Humidity Sensor Compatible With CMOS Technology

Humidity sensors are a kind of important sensors. They are applied to many occasions such as storage, industry manufacture, process control and air-conditioned buildings et al. With the development of science, people need high-powered humidity sensors.As the bulk and surface micromachining techniques are getting mature, the integrated sensors fabricated by industrial CMOS IC technologies have received a great interest. If we integrate the sensor elements and signal processing circuits on a single chip by using CMOS fabrication, we can process the large-scale integration, reduce the cost, minish the size of the whole system and advance the reliability. It is very meaning to research capacitive humidity sensors compatible with CMOS technology.First, we summarize the research meaning of humidity sensors and their types. After comparison of different types of humidity sensor, we analyze the excellence of capacitive humidity sensors compatible with CMOS technology, so we treat them as the research object of this paper. The main research areas of the paper are:First, this capacitive humidity sensor's physical model is built. It uses comb electrodes and polyimide as moisture sensing material. The theoretical model of the capacitive humidity sensor is analyzed. The matlab simulation results show that our model has a better agreement to experiment results than Laconte's model does.Second, we research the theory of operational amplifiers. The two-stage operational amplifier based on 0.6um CSMC library is designed. We simulate this circuit by the Virtuoso of Cadence and get the approving result. It's gain of direct current is 72dB, and it's phase margin is 62°.Third, after comparison of different measuring means of humidity sensor, an optimized measuring circuit has been put forward. The measuring circuits are theoretically deduced. Based on 0.6um CSMC library the measuring circuit is simulated, the results are got by the Virtuoso of Cadence.We introduce the rules of CMOS layout in the fifth chapter of this paper. We design the layout and analyze the post-processing of the capacitive humidity sensor compatible with CMOS technology. It will guarantee a successful tape out of humidity sensor. Finally, we make a summary and show the emphases and the shortage of this paper.