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Development and post-dicing wet release of MEMS magnetometer: an approach

Aditi (Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India and CSIR-Central Electronics Engineering Research Institute, Pilani, India)
Supriyo Das (CSIR-Central Electronics Engineering Research Institute, Pilani, India)
Ram Gopal (CSIR-Central Electronics Engineering Research Institute, Pilani, India)

Microelectronics International

ISSN: 1356-5362

Article publication date: 19 July 2021

Issue publication date: 17 August 2021

101

Abstract

Purpose

Si-based micro electro mechanical systems (MEMS) magnetometer does not require specialized magnetic materials avoiding magnetic hysteresis, ease in fabrication and low power consumption. It can be fabricated using the same processes used for gyroscope and accelerometer fabrication. The paper reports the dicing mechanism for the released MEMS xylophone magnetic sensor fabricated using wafer bonding technology and its characterization in ambient pressure and under vacuum conditions. The purpose of this paper is to dice the wafer bonded Si-magnetometer in a cost-effective way without the use of laser dicing and test it for Lorentz force transduction.

Design/methodology/approach

A xylophone bar MEMS magnetometer using Lorentz force transduction is developed. The fabricated MEMS-based xylophone bars in literature are approximately 500 µm. The present work shows the released structure (L = 592 µm) fabricated by anodic bonding technique using conducting Si as the structural layer and tested for Lorentz force transduction. The microstructures fabricated at the wafer level are released. Dicing these released structures using conventional diamond blade dicing may damage the structures and reduce the yield. To avoid the problem, positive photoresist S1813 was filled before dicing. The dicing of the wafer, filled with photoresist and later removal of photoresist post dicing, is proposed.

Findings

The devices realized are stiction free and straight. The dynamic measurements are done using laser Doppler vibrometer to verify the released structure and test its functionality for Lorentz force transduction. The magnetic field is applied using a permanent magnet and Helmholtz coil. Two sensors with quality factors 70 and 238 are tested with resonant frequency 112.38 kHz and 114.38 kHz, respectively. The sensor D2, with Q as 238, shows a mechanical sensitivity of 500 pm/Gauss and theoretical Brownian noise-limited resolution of 53 nT/vHz.

Originality/value

The methodology and the study will help develop Lorentz force–based MEMS magnetometers such that stiction-free structures are released using wet etch after the mechanical dicing.

Keywords

Acknowledgements

The authors would like to acknowledge Director CEERI for the motivation and support. The authors would like to extend their gratitude to the facility team at CSIR-CEERI, Pilani, to support fabrication. The work was financially supported by CSIR, New Delhi, to carry out the research.

Citation

Aditi, Das, S. and Gopal, R. (2021), "Development and post-dicing wet release of MEMS magnetometer: an approach", Microelectronics International, Vol. 38 No. 2, pp. 60-65. https://doi.org/10.1108/MI-12-2020-0081

Publisher

:

Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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