Fabrication and characteristics of magnetic field sensors based on nano-polysilicon thin-film transistors

A magnetic field sensor based on nano-polysilicon thin films transistors （TFTs） with Hall probes is proposed. The magnetic field sensors are fabricated on （100） orientation high resistivity （p 〉 500 Ω.cm） silicon substrates by using CMOS technology, which adopt nano-polysilicon thin films with thicknesses of 90 nm and heterojunction interfaces between the nano-polysilicon thin films and the high resistivity silicon substrates as the sensing layers. The experimental results show that when VDs = 5.0 V, the magnetic sensitivities of magnetic field sensors based on nano-polysilicon TFTs with length-width ratios of 160 μm/80 μm, 320 μm/80 μm and 480 μm/80 μm are 78 mV/T, 55 mV/T and 34 mV/T, respectively. Under the same conditions, the magnetic sensitivity of the obtained magnetic field sensor is significantly improved in comparison with a Hall magnetic field sensor adopting silicon as the sensing layers.