A single-crystal silicon 3-axis CMOS-MEMS accelerometer

The paper presents a single-crystal silicon (SCS)-based, integrated 3-axis accelerometer fabricated using a post-CMOS micromachining process. This new CMOS-MEMS process provides monolithic integration of electronics and SCS microstructures, and electrical isolation of silicon. By employing a unique vertical sensing mechanism, 3-axis acceleration sensing is achieved with a single proof mass. The symmetric structures and fully differential configuration of all the sensing electrodes can greatly reduce the cross coupling among the 3 axes. By sacrificing one interconnect metal layer, the silicon undercut of the sensing comb fingers is minimized, resulting in much higher sensitivity with the same device footprint. A wet Al etching process was also developed to remove the top Al layer without attacking the Al layers exposed from the sidewalls of the multilayer Al/oxide stacks. A two-stage, open-loop, continuous time chopper stabilized amplifier is integrated on the chip.

[1]  K. Najafi,et al.  A high sensitivity z-axis torsional silicon accelerometer , 1996, International Electron Devices Meeting. Technical Digest.

[2]  Gary K. Fedder,et al.  Design and fabrication of an integrated CMOS-MEMS 3-axis accelerometer , 2003 .

[3]  Junseok Chae,et al.  A monolithic three-axis silicon capacitive accelerometer with micro-g resolution , 2003, TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664).

[4]  Kukjin Chun,et al.  A high performance mixed micromachined differential resonant accelerometer , 2002, Proceedings of IEEE Sensors.

[5]  Hidekuni Takao,et al.  A CMOS integrated three-axis accelerometer fabricated with commercial submicrometer CMOS technology and bulk-micromachining , 2001 .

[6]  Gary K. Fedder,et al.  A CMOS z-axis capacitive accelerometer with comb-finger sensing , 2000, Proceedings IEEE Thirteenth Annual International Conference on Micro Electro Mechanical Systems (Cat. No.00CH36308).

[7]  Bernhard E. Boser,et al.  A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics , 1999, IEEE J. Solid State Circuits.

[8]  Reid R. Harrison,et al.  A low-power, low-noise CMOS amplifier for neural recording applications , 2002, 2002 IEEE International Symposium on Circuits and Systems. Proceedings (Cat. No.02CH37353).

[9]  M. Esashi,et al.  Electrostatically levitated spherical 3-axis accelerometer , 2002, Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266).