A CMOS-MEMS BEOL 2-axis Lorentz-Force Magnetometer with Device-Level Offset Cancellation.

Josep Maria Sánchez-Chiva,Juan Valle,Daniel Fernández,Jordi Madrenas

doi:10.3390/s20205899

Abstract

Lorentz-force Microelectromechanical Systems (MEMS) magnetometers have been proposed as a replacement for magnetometers currently used in consumer electronics market. Being MEMS devices, they can be manufactured in the same die as accelerometers and gyroscopes, greatly reducing current solutions volume and costs. However, they still present low sensitivities and large offsets that hinder their performance. In this article, a 2-axis out-of-plane, lateral field sensing, CMOS-MEMS magnetometer designed using the Back-End-Of-Line (BEOL) metal and oxide layers of a standard CMOS (Complementary Metal–Oxide–Semiconductor) process is proposed. As a result, its integration in the same die area, side-by-side, not only with other MEMS devices, but with the readout electronics is possible. A shielding structure is proposed that cancels out the offset frequently reported in this kind of sensors. Full-wafer device characterization has been performed, which provides valuable information on device yield and performance. The proposed device has a minimum yield of with a good uniformity of the resonance frequency kHz, kHz and quality factor , at ambient pressure. Device sensitivity to magnetic field is fAT at Pa when driven with .

Highlights

In the last years, magnetometers have been introduced in a wide range of applications, increasing their demand and popularity [1]
An out-of-plane, lateral field sensing, 2-axis CMOS-Microelectromechanical Systems (MEMS) magnetometer designed with the BEOL metal layers of a standard CMOS process is proposed
Designing the device using such materials, it is possible to manufacture it next to the electronics, side-by-side on the same die, which would allow the further shrink integrated sensing solutions based on MEMS sensors, as well as improving the yield an reducing the manufacturing cost

Summary

Introduction

Magnetometers have been introduced in a wide range of applications, increasing their demand and popularity [1]. Low end magnetometers in consumer electronic devices, with resolutions around some thousands of nanoTesla, are dominated by Hall sensors, devices based in the magnetoresistive effect (xMR), and Fluxgate sensors [2]. These solutions usually show large offsets and can not be integrated in the same die together with the electronics, requiring to stack multiple dies in a single package. On the other hand, Superconducting Quantum Interference Device (SQUID) magnetometers used in medical and research applications can detect fields below the nanoTesla level, but those sensors need extreme temperature conditions to operate conveniently, making them bulky and impossible to shrink [3]. Because of the Lorentz-force sensing principle, the device sensitivity can be conveniently adjusted by changing the driving current

Results

Discussion

Conclusion