Research On SOI Micro Pressure Sensor Based On MEMS Technology

In this paper,the structure of beam-membrane's micro pressure sensors were designed and fabricated on SOI substrates(n-type Si >100< crystal orientation as device layer)by MEMS technology.The micro pressure sensor was constructed by elastic element and sensitive element.The elastic element was consisted of a square silicon membrane and four short beams,and the Wheatstone bridge was constituted by four serpentine piezoresistors at the root of four short beams,respectively.Based on the piezoresistive effect,the external pressure can be measured.Compared with C-type membrane,E-type membrane and other silicon membrane structures,the structure of beam-membrane can produce the stress distribution concentration effect when it is subjected to micro pressure.Through the plane stress concentration effect,the sensitivity of the pressure sensor was greatly improved,and the measurement of the micro pressure(0kPa-10kPa)can be realized.Based on the structure and working principle of sensor,the ANSYS finite element software was used to construct the simulation model of sensors.The influence of silicon membrane structure on pressure sensitive characteristics of sensors were studied,and the model of optimized geometric structure was given.The simulation results showed that the beam-membrane structure had better pressure sensitive characteristics because of the stress concentration distribution effect.In this paper,the influence of the beam-membrane structure parameters on the pressure sensitive characteristics were further simulated and analyzed,and the optimized geometric structure parameters were given.In this paper,the chip layout was designed by L-Edit software,and the manufacturing and packaging of the micro pressure sensor was realized on the SOI chip by MEMS technology.The characteristics of micro pressure sensors were studied by the automatic pressure transmitter test system,the high and low temperature experiment box and pressure test disk.Experimental results show: when the power supply voltage was 5.0 V and the pressure range was 0kPa-10 kPa,the micro pressure sensor with beam-membrane structure of sensitivity was 0.473 m V/kPa,the linearity was0.105%F.S.,the repeatability was 0.316%F.S.,the hysteresis was 0.211%F.S.,theaccuracy was 0.394%F.S.,at room temperature of 20?;the sensitivity temperature drift of the micro pressure sensor is-25 ppm/? with the temperature range from-40? to85?.