MOS-gated bipolar Magnetotransistors for 360° angular sensing

Abstract

Bipolar npn Lateral MagnetoTransistors (LMTs) are attractive for in-plane magnetic-field sensing, but suffer from large offset. In this paper we introduce LMTs with several new features: (1) usage of a CMOS-SOI process (no substrate leakage), (2) two central emitters for smaller offset, and (3) emitter (E), base (B), and collector (C) contact definition by MOS-gate structures giving lower random fluctuations than Shallow Trench Insulation (STI). By TCAD simulation, modelling and sensor characterization of wafer-level and packaged samples, the sensitivity and offset of various LMT types are assessed over the automotive temperature range from -40°C to 150°C. A highly accurate 360° angular sensor for automotive applications is feasible when two LMT quadrant detectors are combined with an anisotropic magnetoresistance (AMR) 180° sensor using single or dual temperature calibration.