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Semiconductor pressure sensors have better characteristics than conventional pressure sensors, such as high sensitivity, high accuracy, no hysteresis, small size and on-chip, to recommend their useful in a wide field. Ongoing advances in IC fabrication technology, semiconductor pressure sensors have become to the major objective of manufacture already. The sensitivity of a silicon pressure sensor is influenced by the geometry structure of thin diaphragm, piezoresistor layout and piezorestive coefficients.Therefore, the semiconductor pressure sensors which the diaphragm has a uniform, smooth, well- controlled thickness dimension and low resistivity of the piezoresistors are helpful to promote the performance of the sensors. Recently, there are many reports about improving the sensitivity and other important parameter of the silicon pressure sensors by utilizing special geometry structure. From this point of view, the objective of the paper focus on the fabrication and characterization of JFET pressure sensors,which replace four resistors by JFET in the form of a Wheatston bridge, its voltage-variable-resistance effect can improve the performance of the sensor. In this experiment, the process design, precision control of diaphragm thickness, the parameters which may influence the output voltage (sensitivity and Voffset) of sensors including the diaphragm thickness,piezoresistors layout, dopant concentration and pn junction of JFET etc. are discussed. On the precision control of diaphragm thickness, we use 85C、45%wt、KOH etchant which has different etch rate for Si and SiO2 to make a thin square diaphragm (1mm length and 15um thickness) and alignment window simultaneously, then JFET can be diffused on the correct position of diaphragm and crystallographic line. On the measurement of sensitivity, it can be increased (Normalize Sensitivity from 1 to 1.08) by increasing gate voltage (Vgs from 0V to 2V) or it can be increased(Normalize Sensitivity from 1 to 1.03) by increasing input voltage (Vin from 1V to 5V). On the measurement of zero-pressure offset voe (Voffset), it can be compensated for adjusting the gate voltage or increasing input voltage.
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