A novel 3-D magnetic-field sensor in standard CMOS technology

Measurement of the three components of the magnetic-field vector simultaneously, by an integrated magnetic-field sensor, has many practical applications. In this paper we present a three-dimensional (3-D) magnetic-field sensor in standard 2 μm CMOS technology. The sensor uses two CMOS-compatible one-dimensional vertical magnetotransistors positioned at right angles to each other to measure two field components; a MAGFET and/or a lateral bipolar transistor is used to measure the third component. To minimize the offset due to asymmetry during fabrication, two base contacts are used. The MOS device controls the base surface potential and thereby improves the device characteristics and the noise performance in the lateral device. The device is designed and fabricated by MOSIS using standard p-well technology. Simulations are performed to study the electrical characteristics and to find out the optimized geometry in order to achieve high current gain by using PISCES-IIBa 2-D device simulation software. The measured device characteristics show relative sensitivities S_xx = 7.19 × 10^-7 G^-1, S_yy = 1.88 × 10^-6 G^-1 and S_zz = 6.80 × 10^-7 G^-1 in the X-, Y- and Z-directions respectively, to the applied magnetic field.