High-Resolution Capacitive Microinclinometer With Oblique Comb Electrodes Using (110) Silicon

We propose a new capacitive microinclinometer where oblique comb electrodes and double-folded suspension springs are aligned parallel to the vertical (111) plane of (110) silicon. The oblique comb utilizes both the overlapped area and the gap between movable and stationary electrodes, resulting in a considerable increase in sensitivity (capacitance change/angle). The resolution becomes even higher by taking advantage of the smooth (111) sidewalls of the oblique comb electrodes, which are fabricated using silicon deep reactive ion etching followed by crystalline wet etching. The surface roughness was reduced from 200 (Rrms) to 20 nm (Rrms), and the verticality was improved from 88.7° to 89.7°. The capacitance change of the fabricated inclinometer experimentally ranges from -0.793 to 0.783 pF for the full range of inclination angle (from -90° to 90°). The estimated worst resolution, which is obtainable at an inclination angle of ±85°, was as low as 0.25°.

[1]  R B Stein,et al.  Application of tilt sensors in functional electrical stimulation. , 1996, IEEE transactions on rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society.

[2]  Jong-Hyun Lee,et al.  Fabrication of vertical optical plane using DRIE and KOH crystalline etching of (110) silicon wafer , 2006 .

[3]  F. Ayazi.  A high aspect-ratio high-performance polysilicon vibrating ring gyroscope. , 2000 .

[4]  L. Zhao,et al.  Micro Capacitive Tilt Sensor for Human Body Movement Detection , 2007, BSN.

[5]  Myung-Lae Lee,et al.  Novel Micro Capacitive Inclinometer with Oblique Comb Electrode and Suspension Spring Aligned Parallel to {111} Vertical Planes of (110) Silicon , 2009, 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems.

[6]  Mona E. Zaghloul,et al.  Convection-Based Accelerometer and Tilt Sensor Implemented in Standard CMOS , 1998 .

[7]  S. Kal,et al.  Etch characteristics of KOH, TMAH and dual doped TMAH for bulk micromachining of silicon , 2006, Microelectron. J..

[8]  T. Gabrielson.  Mechanical-thermal noise in micromachined acoustic and vibration sensors , 1993 .

[9]  Aleksandar Milenkovic,et al.  System architecture of a wireless body area sensor network for ubiquitous health monitoring , 2005 .

[10]  Myung-Lae Lee,et al.  Fabrication of morphological defect-free vertical electrodes using a (1 1 0) silicon-on-patterned-insulator process for micromachined capacitive inclinometers , 2009 .

[11]  Yong-Kweon Kim,et al.  A high-aspect-ratio comb actuator using UV-LIGA surface micromachining and (110) silicon bulk micromachining , 2002 .

[12]  Chang Jin Kim,et al.  An optimized MEMS-based electrolytic tilt sensor , 2007 .

[13]  Walter Lang,et al.  Micromachined inclinometer with high sensitivity and very good stability , 2002 .

[14]  Haluk Kulah,et al.  A CMOS-compatible high aspect ratio silicon-on-glass in-plane micro-accelerometer , 2005 .

[15]  M. Bodnicki,et al.  Sensing Tilt With MEMS Accelerometers , 2006, IEEE Sensors Journal.

[16]  H. Seidel,et al.  Safety relevant microsystems for automotive applications , 1998, MHA'98. Proceedings of the 1998 International Symposium on Micromechatronics and Human Science. - Creation of New Industry - (Cat. No.98TH8388).

[17]  Richard Dixon,et al.  Markets and applications for MEMS inertial sensors , 2006, SPIE MOEMS-MEMS.

[18]  K. Najafi,et al.  A monolithic three-axis micro-g micromachined silicon capacitive accelerometer , 2005, Journal of Microelectromechanical Systems.