Fabrication And Characteristics Of High Sensitivity Magnetic Sensor Based On Nano - Silicon Thin Film Transistor

This article shows a high sensitivities magnetic field sensor based on the nc-Si thinfilm transistors, this sensor contains the source(S), drain(D), gate(G) and the Hall outputprobes (VH1and VH2) on both sides of the channel from the drain channel length of0.5times, by adopting the nc-Si thin films channel layers and the nc-Si/high resistivitysilicon heterojunction interfaces as the magnetic sensing layers, detection of externalmagnetic field can be realized. Nc-Si thin films were studied and deposited on the<100> orientation high resistivity silicon substrates by using an low pressure chemicalvapor deposition system (LPCVD), by X-ray diffraction (XRD) analysis, three Sidiffraction peaks of the nc-Si thin films were formed, crystal orientations of thediffraction peaks correspond to the <111>,<220> and <311>, respectively, preferredcrystal orientation is <220>. It is observed that as the thin film thickness increases withthe increase of Si diffraction peaks, the analysis of scanning electron microscope (SEM)shows nc-Si thin films is composed by nano-grain of different crystal orientation andgrain boundary, as the thin film thickness increases, the grain size increases gradually.On the basis of nc-Si thin film research, in this article, the high sensitivities magneticsensor was fabricated on <100> orientation high resistivity silicon through using CMOStechnology. At room temperature, the static characteristics of the magnetic sensor weremeasured by a magnetic field generator(CH-100), precise constant current and constantvoltage supply(PSW80-13.5), and multimeter(Agilent34401A), the study of sensitivitycharacteristic of magnetic field sensor is focused on the influence of the substrate type,the size of the channel, the thickness of nc-Si thin film, doping type and the dose of theimplanted ions, respectively. When channel length-width ratio, thickness of nc-Si thinfilm, doping type and dose of the implanted ions are320μm/160μm,120nm, n typeand5×1012atom/cm2, respectively, at VDS=5.0V, the maximum magnetic sensivitity of the sensor is264.2mV/T, linearity, reaptability, hystersis and accuracy of the sensor are0.19%F.S.,0.28%F.S.,0.55%F.S. and0.64%F.S., respectively. The experimental resultsshow the magnetic sensitivity is significantly improved through this structure.