Temperature Compensation Integration Research Based On Asymmetric Base Region Transistor Pressure Sensor

In this paper, the base asymmetric transistor temperature compensating pressure sensors were designed and fabricated on SOI substrates(n-type Si <100> crystal orientation with high resistivity as device layer) by bipolar technology and MEMS technology. The pressure sensitive structure was constructed by C-type Si cup and the Wheatstone bridge that constitute by four p-type diffused resistances on the square silicon membrane, the part of temperature compensating contains the base asymmetric transistor. The square silicon membrane is been elastic deformation caused by the applied pressure P and the output voltage of Wheatstone bridge is changed. Theoretical analysis shows, the applied pressure P can be measured by the pressure sensitive structure. The structure of base asymmetric transistor is adopted to realize temperature compensating since the negative temperature coefficient of the p-n junction, the compensation effect can be controlled by the ratio of the base resistance. The simulation model were builded by ANSYS software, in order to study the influence of the shape and size of the silicon membrane on the characteristics of the sensor. With the help of MATLAB, the position of the resistances' distribution on the square silicon membrane were calculated and the optimized of the temperature compensating pressure sensor is gaven.In this paper, the chip layout was designed by L-Edit software, and the manufacturing and packaging of the temperature compensating pressure sensor is realized on the SOI chip. The characteristics of temperature compensating pressure sensor with base asymmetric transistor were studied by the automatic pressure transmitter test system(American Mensor CPC6000) and the high and low temperature experiment box(OBIS GDJS-100LG-G). Experimental results shows: when the power supply voltage is 5.0 V the pressure sensor sensitivity is 0.227 m V/k Pa, at room temperature; the sensitivity temperature drift of the pressure sensor is-1067 ppm/? with the temperature range from-40? to 100?, and the sensitivity temperature drift of the temperature compensating pressure sensor is-1067 ppm/?; after the optimizing the base asymmetric transistor, the sensitivity temperature drift of the temperature compensating pressure sensor is-127 ppm/ ?. The results demonstrate that, the temperature compensating pressure sensor which designed and fabricated in this paper has good pressure sensitivity and temperature characteristics.