Fabrication and characterization of an SOI MEMS gyroscope

Weiwei Zhong; Guowei Han; Chaowei Si; Jin Ning; Fuhua Yang

doi:10.1088/1674-4926/34/6/064004

J. Semicond. > 2013, Volume 34 > Issue 6 > 064004

SEMICONDUCTOR DEVICES

Fabrication and characterization of an SOI MEMS gyroscope

Weiwei Zhong^{1, 2}, Guowei Han^{1, 2}, Chaowei Si^{1, 2}, Jin Ning^{1, 2,} and Fuhua Yang^{1, 2}

+ Author Affiliations

Corresponding author: Ning Jin, Email:ningjin@semi.ac.cn

DOI: 10.1088/1674-4926/34/6/064004

Abstract: This paper presents an SOI (silicon on insulator) MEMS (micro-electro-mechanical systems) vibratory gyroscope that was fabricated using bulk micromachining processes. In the gyroscope architecture, a frame structure that nests the proof mass is used to decouple the drive motion and sense motion. This approach ensures that the drive motion is well aligned with the designed drive axis, and minimizes the actual drive motion component along the sense detection axis. The thickness of the structural layer of the device is 100 μm, which induces a high elastic stiffness in the thickness direction, so it can suppress the high-order out-of-plane resonant modes to reduce deviation. In addition, the dynamics of the gyroscope indicate that higher driving mass brings about higher sensing displacements. The thick structural layer can improve the output of the device by offering a sufficient mass weight and large sensing capacitance. The preliminary test results of the vacuum packaged device under atmospheric pressure will be provided. The scale factor is 1.316×10^-4 V/(deg/s), the scale factor nonlinearity and asymmetry are 1.87% and 0.36%, the zero-rate offset is 7.74×10^-4 V, and the zero-rate stability is 404 deg/h, respectively.

Key words: SOI MEMS vibratory gyroscope, bulk micromachining processes, decoupled gyroscope, ICP

References

[1]	Alper S E, Temiz Y, Akin T. Effect of quadrature error on the performance of a fully-decoupled MEMS gyroscope. IEEE 24th International Conference on Micro Electro Mechanical Systems (MEMS), 2011:569 http://ieeexplore.ieee.org/document/5734488/
[2]	Acar C, Shkel A. MEMS vibratory gyroscopes structural approaches to improve robustness. Springer, 2009 http://ci.nii.ac.jp/ncid/BA90485964
[3]	Liu K, Zhang W P, Chen W Y, et al. The development of micro-gyroscope technology. J Micromechan Microeng, 2009, 19:113001 doi: 10.1088/0960-1317/19/11/113001
[4]	Saleem M M, Bazaz S A. Design and robustness analysis of structurally decoupled 3-DoF MEMS gyroscope in the presence of worst-case process tolerances. Microsystem Technologies-Micro-and Nanosystems-Information Storage and Processing Systems, 2011, 17:1381 doi: 10.1007/s00542-011-1315-x?no-access=true
[5]	Yang B, Yong Y, Huang L, et al. Research on a new decoupled dual-mass micro-gyroscope. The Tenth International Conference on Electronic Measurement & Instruments, 2011:205 http://ieeexplore.ieee.org/abstract/document/6037714/
[6]	Alper S E, Akin T. Symmetrical and decoupled nickel microgyroscope on insulating substrate. Sensors and Actuators A:Physical, 2004, 115:336 doi: 10.1016/j.sna.2004.04.041
[7]	Alper S E, Temiz Y, Akin T. A compact angular rate sensor system using a fully decoupled silicon-on-glass MEMS gyroscope. J Microelectromechan Syst, 2008, 17:1418 doi: 10.1109/JMEMS.2008.2007274
[8]	Liu X S, Yang Z C, Chi X Z, et al. A doubly decoupled lateral axis micromachined gyroscope. Sensors and Actuators A:Physical, 2009, 154:218 doi: 10.1016/j.sna.2008.10.015
[9]	Geiger W, Butt W U, Gaiber A, et al. Decoupled microgyros and the design principle DAVED. Sensors and Actuators A:Physical, 2002, 95:239 doi: 10.1016/S0924-4247(01)00732-4
[10]	Bu M, Melvin T, Ensell G J, et al. A new masking technology for deep glass etching and its microfluidic application. Sensors and Actuators A:Physical, 2004, 115:476 doi: 10.1016/j.sna.2003.12.013
[11]	Iliescu C, Chen B, Miao J. Deep wet etching-through 1 mm pyrex glass wafer for microfluidic applications. IEEE 20th International Conference on Micro Electro Mechanical Systems, 2007:393 http://ieeexplore.ieee.org/document/4433150/?reload=true&arnumber=4433150
[12]	IEEE Standard Specification Format Guide and Test Procedure for Coriolis Vibratory Gyros. Dec 20, 2004: 1
[13]	Li Y, Zhang X, Mumford P, et al. Allan variance analysis on error characters of MEMS inertial sensors for FPGA-based GPS/INS system.

Fig. 1. The layout of the SOI MEMS gyroscope.

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Fig. 2. The fabrication process flow of the SOI MEMS gyroscope. (a) The bonding area forming on the glass substrate (500 $\mu $m). (b) The pattern Al film (100 nm) on the SOI epitaxial layer (100 $\mu$m). (c) Glass and SOI wafer anodic bonding. (d) TMAH etching of the SOI substrate (500 $\mu$m). (e) Electrode metal pad making (Al 500 nm). (f) The pattern silicon dioxide (50 nm) for ICP etching. (g) Thorough silicon ICP etching. (h) The Al film and silicon dioxide removal.

DownLoad: Full-Size Img PowerPoint

Fig. 3. SEM of the SOI MEMS gyroscope.

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Fig. 4. The test board of the MEMS gyroscope.

DownLoad: Full-Size Img PowerPoint

Fig. 5. The measured output at an angular velocity of -10 deg/s

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Fig. 6. The measured response curve specifying the scale factor, the zero-rate offset, and the nonlinearity.

DownLoad: Full-Size Img PowerPoint

Table 1. The test conditions of the gyroscope.

Table 2. The scale factor set parameters.

Table 3. The zero-rate offset set parameters.

[1]	Alper S E, Temiz Y, Akin T. Effect of quadrature error on the performance of a fully-decoupled MEMS gyroscope. IEEE 24th International Conference on Micro Electro Mechanical Systems (MEMS), 2011:569 http://ieeexplore.ieee.org/document/5734488/
[2]	Acar C, Shkel A. MEMS vibratory gyroscopes structural approaches to improve robustness. Springer, 2009 http://ci.nii.ac.jp/ncid/BA90485964
[3]	Liu K, Zhang W P, Chen W Y, et al. The development of micro-gyroscope technology. J Micromechan Microeng, 2009, 19:113001 doi: 10.1088/0960-1317/19/11/113001
[4]	Saleem M M, Bazaz S A. Design and robustness analysis of structurally decoupled 3-DoF MEMS gyroscope in the presence of worst-case process tolerances. Microsystem Technologies-Micro-and Nanosystems-Information Storage and Processing Systems, 2011, 17:1381 doi: 10.1007/s00542-011-1315-x?no-access=true
[5]	Yang B, Yong Y, Huang L, et al. Research on a new decoupled dual-mass micro-gyroscope. The Tenth International Conference on Electronic Measurement & Instruments, 2011:205 http://ieeexplore.ieee.org/abstract/document/6037714/
[6]	Alper S E, Akin T. Symmetrical and decoupled nickel microgyroscope on insulating substrate. Sensors and Actuators A:Physical, 2004, 115:336 doi: 10.1016/j.sna.2004.04.041
[7]	Alper S E, Temiz Y, Akin T. A compact angular rate sensor system using a fully decoupled silicon-on-glass MEMS gyroscope. J Microelectromechan Syst, 2008, 17:1418 doi: 10.1109/JMEMS.2008.2007274
[8]	Liu X S, Yang Z C, Chi X Z, et al. A doubly decoupled lateral axis micromachined gyroscope. Sensors and Actuators A:Physical, 2009, 154:218 doi: 10.1016/j.sna.2008.10.015
[9]	Geiger W, Butt W U, Gaiber A, et al. Decoupled microgyros and the design principle DAVED. Sensors and Actuators A:Physical, 2002, 95:239 doi: 10.1016/S0924-4247(01)00732-4
[10]	Bu M, Melvin T, Ensell G J, et al. A new masking technology for deep glass etching and its microfluidic application. Sensors and Actuators A:Physical, 2004, 115:476 doi: 10.1016/j.sna.2003.12.013
[11]	Iliescu C, Chen B, Miao J. Deep wet etching-through 1 mm pyrex glass wafer for microfluidic applications. IEEE 20th International Conference on Micro Electro Mechanical Systems, 2007:393 http://ieeexplore.ieee.org/document/4433150/?reload=true&arnumber=4433150
[12]	IEEE Standard Specification Format Guide and Test Procedure for Coriolis Vibratory Gyros. Dec 20, 2004: 1
[13]	Li Y, Zhang X, Mumford P, et al. Allan variance analysis on error characters of MEMS inertial sensors for FPGA-based GPS/INS system.

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Received: 31 October 2012 Revised: 16 January 2013 Online: Published: 01 June 2013

This paper presents an SOI (silicon on insulator) MEMS (micro-electro-mechanical systems) vibratory gyroscope that was fabricated using bulk micromachining processes. In the gyroscope architecture, a frame structure that nests the proof mass is used to decouple the drive motion and sense motion. This approach ensures that the drive motion is well aligned with the designed drive axis, and minimizes the actual drive motion component along the sense detection axis. The thickness of the structural layer of the device is 100 μm, which induces a high elastic stiffness in the thickness direction, so it can suppress the high-order out-of-plane resonant modes to reduce deviation. In addition, the dynamics of the gyroscope indicate that higher driving mass brings about higher sensing displacements. The thick structural layer can improve the output of the device by offering a sufficient mass weight and large sensing capacitance. The preliminary test results of the vacuum packaged device under atmospheric pressure will be provided. The scale factor is 1.316×10^-4 V/(deg/s), the scale factor nonlinearity and asymmetry are 1.87% and 0.36%, the zero-rate offset is 7.74×10^-4 V, and the zero-rate stability is 404 deg/h, respectively.

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