The Study Of Piezoresistive MEMS Acoustic Sensor

The rapid development of integrated circuit and Micro-electro mechanical system technology(MEMS) accelerates the research and application of the silicon mic-rosensor. In this paper, the Micro-electro mechanical system(MEMS) acoustic sensor is studied and, the MEMS acoustic sensor chip is designed as per the operating principles and the structural characteristics of MEMS acoustic sensor. The acoustic sensor chip is also simulated by the finite element analysis software. The simulation results meet with the requirements of the research objective. In the meanwhile, in this paper, it is also analyzed and discussed the package structure, fabrication process, processing circuit and test data of the MEMS acoustic sensor.MEMS acoustic sensor is composed of the pressure sensitive film structure and the four voltage dependent resistors, based on the pezoresistivity. It is applied SOI silicon chips, fabricated by the micro machining technology. The pressure sensitive film structure and the voltage dependent resistors of MEMS acoustic sensor are designed out, by modeling and simulation on the finite element software. The four voltage dependent resistors on the pressure sensitive film structure constitute the Wheatstone bridge. By the action of the sound pressure, the two voltage dependent resistors' values on the Wheatstone bridge become greater, while the other two voltage dependent resistors' values become smaller. Herein, one voltage signal is generated from the Wheatstone bridge. This v oltage signal varies directly proportional to the sound pressure. In this paper, the four voltage dependent resistors are made out on the SOI Silicon chip, by the photolithography technique and ion implantation technology etc; the pressure sensitive film structure is made out by the application of the ICP deep groove etching technique. In order to make the test and analysis for the MEMS acoustic sensor's performance, the signal processing circuit is designed, which has these functions: amplifying, filtering, compensating.In this paper, the actual test results of the MEMS acoustic sensor are shown as below: its sound pressure working range is 130 d B~150d B; zero output is 2.5V; sensitivity coefficient is 2.658 m V/Pa; frequency response is 50Hz~6000Hz; working temperature is-40?~125?. The test results for the MEMS acoustic sensor meet with the requirements of the research objective.