Inverted Pyramid 3-axis Silicon Hall Effect Magnetic Sensor With Offset Cancellation

TL;DR

This paper presents a novel 3-axis silicon Hall-effect magnetic sensor with an inverted pyramid structure, achieving high sensitivity, low offset, and compact design suitable for diverse applications.

Contribution

The paper introduces a new 3-axis Hall-effect sensor using MEMS and CMOS processes with offset cancellation, enhancing performance and integration.

Findings

High sensitivities ranging from 64.1 to 198 V A$^{-1}$ T$^{-1}$

Offset reduced by one to three orders of magnitude

Crosstalk below 3.7% and low thermal noise floor

Abstract

Microelectronic magnetic sensors are essential in diverse applications, including automotive, industrial, and consumer electronics. Hall-effect devices hold the largest share of the magnetic sensor market, and they are particularly valued for their reliability, low cost and CMOS compatibility. This paper introduces a novel 3-axis Hall-effect sensor element based on an inverted pyramid structure, realized by leveraging MEMS micromachining and CMOS processing. The devices are manufactured by etching the pyramid openings with TMAH and implanting the sloped walls with n-dopants to define the active area. Through the use of various bias-sense detection modes, the device is able to detect both in-plane and out-of-plane magnetic fields within a single compact structure. In addition, the offset can be significantly reduced by one to three orders of magnitude by employing the current-spinning method. The device presented in this work demonstrated high in-plane and out-of-plane current- and voltage-related sensitivities ranging between 64.1 to 198 V A$^{-1}$ T$^{-1}$ and 14.8 to 21.4 mV V$^{-1}$ T$^{-1}$, with crosstalk below 3.7 %. The sensor exhibits a thermal noise floor which corresponds to approximately 0.5 $\mu$T/$\sqrt{Hz}$ at 1.31 V supply. This novel Hall-effect sensor represents a promising and simpler alternative to existing state-of-the-art 3-axis magnetic sensors, offering a viable solution for precise and reliable magnetic field sensing in various applications such as position feedback and power monitoring.