Sensitivity Improvement of a Fully Symmetric Vertical Hall Device Fabricated in 0.18 μm Low-Voltage CMOS Technology

Abstract

This paper proposes a new implementation method to significantly improve the magnetic sensitivity of a fully symmetric vertical Hall device (FSVHD) based on low-voltage CMOS technology. The FSVHD consists of four identical three-contact vertical Hall elements (3CVHE) and each 3CVHE is located in a low-doped deep n-well. The terminals of the 3CVHE are $\text{n}^{+}$ implanted in an n-well and a $\text{p}^{+}$ implantation in a p-well is performed to act as a trench between two adjacent $\text{n}^{+}$ contacts, enabling Hall current flowing deeply for sensitivity improvement. The influence of the geometry sizes on magnetic sensitivity is exploited utilizing TCAD simulation to obtain the optimized device structure in a $0.18~\mu\text{m}$ CMOS standard technology. The experimental results reveal that the proposed FSVHD with a $\text{p}^{+}$ /p-well trench can attain an improved voltage-related sensitivity of 8.4 mV/VT, which is about 70% higher than that of a conventional FSVHD without a trench in the same CMOS fabrication process, while offset and noise are not degraded. The proposed $\text{p}^{+}$ /p-well implantation trench is a good solution to enhance the sensitivity of a low-voltage CMOS VHD with a low manufacturing cost.

Keywords

• Vertical hall device
• magnetic sensitivity
• trench
• standard CMOS 14 technology