SIMULATION STUDY OF CONVEX CORNER UNDERCUTTING IN KOH AND TMAH FOR A MEMS PIEZORESISTIVE ACCELEROMETER
DOI:
https://doi.org/10.11113/jt.v78.4914Keywords:
Convex corner undercutting, MEMS piezoresistive accelerometer, Intellisuite CAD, KOH, TMAHAbstract
Undercutting is a common problem in wet anisotropic etching. This problem in turn, influences the performance and sensitivity of MEMS devices. This paper investigates the use of corner compensation to prevent convex corner undercutting in a MEMS piezoresistive accelerometer. The Intellisuite CAD simulation software was used for designing the mask with corner compensation and for analysing wet anisotropic etching profiles in potassium hydroxide (KOH) and tetra-methyl-ammonium-hydroxide (TMAH) solutions at different concentrations and temperatures. Perfect 90 degrees corners on the proof mass was successfully etched using a corner compensation design at etching temperature of 63 °C for KOH and 67.7 °C for TMAH with 25 wt% and 10.3 wt% concentration levels, respectively. Etching in TMAH required lower concentration level, thus making the etching process safer. However, TMAH required longer time to etch perfect convex corners compared to KOH. Nevertheless, both KOH and TMAH etchants have been successfully used to etch perfect convex corners by using the designed corner compensation mask. Â
References
A. Ravi Sankar, S. Das, and S. K. Lahiri. 2008. Cross-axis Sensitivity Reduction Of A Silicon MEMS Piezoresistive Accelerometer. Microsystem Technology. 15(4): 511-518.
A. Ravi Sankar, J. G. Jency, J. Ashwini, and S. Das. 2012. Realisation Of Silicon Piezoresistive Accelerometer With Proof Mass-Edge-Aligned-Flexures Using Wet Anisotropic Etching. Micro & Nano Letters. 7: 118-121
S. Dutta, M. Imran, P. Kumar, R. Pal, P. Datta, and R. Chatterjee. 2011. Comparison Of Etch Characteristics Of KOH, TMAH And EDP For Bulk Micromachining Of Silicon (110). Microsystem Technology. 17(10-11): 1621-1628.
K. Biswas and S. Kal. 2006. Etch characteristics of KOH, TMAH And Dual Doped TMAH For Bulk Micromachining Of Silicon. Microelectronics J. 37(6): 519-525.
Norhayati Soin and Burhanuddin Y.Majlis. 2006. Characterization of Anisotropic Etching Effects of KOH Concentration and Temperature on Etching Profiles Properties of Silicon Corrugated Diaphragm. American Institute of Physics Conference Proceedings, 2006. 909: 128-132.
P. Pal, S. Haldar, S. S. Singh, A Ashok, X. Yan, and K. Sato. 2014. A Detailed Investigation And Explanation Of The Appearance Of Different Undercut Profiles in KOH and TMAH. J. Micromechanics Microengineering. 24(9): 095026
X. P. Wu and W. H. Ko. 1989. Compensating Corner Undercutting In Anisotropic Etching Of (100) Silicon. Sensors and Actuators. 18(2): 207-215.
P. Pal, K. Sato, and S. Chandra. 2007. Fabrication Techniques Of Convex Corners In A (1 0 0)-Silicon Wafer Using Bulk Micromachining: A Review. J. Micromechanics Microengineering. 17(10): R111-R133.
Prem Pal and Sudhir Chandra. 2004. A Novel Process For Perfect Convex Corner Realization In Bulk Micromachining. J. Micromechanis Microengineering. 14: 1416-1420.
M. M. Smiljanić, V. Jović, and Ž. Lazić. 2012. Maskless Convex Corner Compensation Technique On A (1 0 0) Silicon Substrate In A 25 %Wt TMAH Water Solution. J. Micromechanics Microengineering. 22(11): 115011.
B. Tang, K. Sato, S. Xi, G. Xie, D. Zhang, and Y. Cheng. 2014. Process Development Of An All-Silicon Capacitive Accelerometer With A Highly Symmetrical Spring-Mass Structure Etched In TMAH+Triton-X-100. Sensors Actuators:A Physical. 217: 105-110.
M. H. M. Khir, P. Qu, and H. Qu. 2011. A Low-Cost CMOS-MEMS Piezoresistive Accelerometer With Large Proof Mass. Sensors. 11(8): 7892-907.
R. P. Van Kampen and R. F. Wolffenbuttel. 1998. Modeling The Mechanical Behavior Of Bulk-Micromachined Silicon Accelerometers. Sensors and Actuators A. 64: 137-150.
R. Mukhiya, a. Bagolini, T. K. Bhattacharyya, L. Lorenzelli, and M. Zen. 2011. Experimental Study And Analysis Of Corner Compensation Structures For CMOS Compatible Bulk Micromachining Using 25%wt TMAH. Microelectronics J. 42(1): 127-134.
N. Soin and Burhanudin Y. Majlis. 2005. KOH Etching Process Of Perfect Square MEMS Corrugated Diaphragm. Proceeding of Device and Process Technologies for Microelectronics, MEMS, and Photonics IV. 6037: 60371Z-60371Z-10.
N. Yusof, A. C. W. Noorakma, and N. Soin. 2014. Corner Compensation Mask Design On (MEMS) Accelerometer Structure. IEEE International Conference Semiconductor Electron, 2014. 248-251.
M. Shikida, K. Sato, K. Tokoro, and D. Uchikawa. 1999. Comparison Of Anisotropic Etching Properties Between KOH And TMAH Solutions. International Conference on Micro Electro Mechanical Systems,1999. 315-320.
N. Soin and B. Y. Majlis. 2006. Development Of Perfect Silicon Corrugated Diaphragm Using Anisotropic Etching. Microelectronic Engineering. 83: 1438-1441.
Downloads
Published
Issue
Section
License
Copyright of articles that appear in Jurnal Teknologi belongs exclusively to Penerbit Universiti Teknologi Malaysia (Penerbit UTM Press). This copyright covers the rights to reproduce the article, including reprints, electronic reproductions, or any other reproductions of similar nature.
