Differential Structure and Characteristics of a New-Type Silicon Magnetic Sensitivity Transistor

A differential structure magnetic sensor is proposed.It is comprised of two new-type silicon magnetic sensitivity transistors(SMSTs)with similar characteristics and has a common emitter,two bases and two collectors.The sensor is fabricated by micro electromechanical system technology on a<100>high resistivity silicon wafer.At room temperature,when supply voltage VDD=10.0 V,all the base currents Ib1 of SMST1 and Ib2 of SMST2 equal 6.0 mA,the absolute magnetic sensitivity for the two SMSTs are 46.8 mV/kG and 56.1 mV/kG,respectively,and the absolute magnetic sensitivity for the sensor is 102.9 mV/kG.Meanwhile,the temperature coefficientαV of the collector output voltage of the sensor is 0.044%/℃.The experimental results show that the magnetic sensitivity and the temperature characteristics of the sensor can be improved and ameliorated compared with a single SMST.

Fabrication and characterization of the split-drain MAGFET based on the nano-polysilicon thin film transistor

A split-drain magnetic field-effect transistor （MAGFET） based on a nano-polysilicon thin film transistor （TFT） is proposed, which contains one source, two drains and one gate. The sensor chips were fabricated on （100） high resistivity silicon substrate by CMOS technology. When drain-source voltage equals 5.0 V and length and width ratio of the TFT channel is 80 μm/160 μm, the current and voltage magnetic sensitivities of the split-drain MAGFET based on the TFT are 0.018 mA/T and 55 mV/T, respectively. Through adopting nano-polysilicon thin films and nano-polysilicon thin films/high resistivity silicon heterojunction interfaces as the magnetic sensing layers, it is possible to realize detection of the external magnetic field. The test results show that magnetic sensitivity of the split-drain MAGFET can be improved significantly.