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Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110)

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Abstract

Bulk micromachining in Si (110) wafer is an essential process for fabricating vertical microstructures by wet chemical etching. We compared the anisotropic etching properties of potassium hydroxide (KOH), tetra-methyl ammonium hydroxide (TMAH) and ethylene di-amine pyro-catechol (EDP) solutions. A series of etching experiments have been carried out using different etchant concentration and temperatures. Etching at elevated temperatures was found to improve the surface quality as well as shorten the etching time in all the etchants. At 120°C, we get a smooth surface (Ra = 21.2 nm) with an etching rate 12.2 μm/min in 40wt% KOH solution. At 125°C, EDP solution (88wt%) was found to produce smoothest surface (Ra = 9.4 nm) with an etch rate of 1.8 μm/min. In TMAH solution (25wt%), the best surface roughness was found to be 35.6 nm (Ra) at 90°C with an etch rate of 1.18 μm/min. The activation energy and pre-exponential factor in Arrhenius relation are also estimated from the corresponding etch rate data.

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Acknowledgments

The authors acknowledge Director SSPL for his continuous support and for the permission to publish this work. Help from other colleagues in optical analysis and DekTak are also acknowledged.

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Authors and Affiliations

  1. Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi, 110054, India

    Shankar Dutta, Md Imran, P. Kumar, R. Pal & P. Datta

  2. Indian Institute of Technology, Hauz Khas, New Delhi, 110016, India

    R. Chatterjee

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  1. Shankar Dutta
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  2. Md Imran
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  3. P. Kumar
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  4. R. Pal
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  5. P. Datta
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  6. R. Chatterjee
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Correspondence to Shankar Dutta.

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Dutta, S., Imran, M., Kumar, P. et al. Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110). Microsyst Technol 17, 1621 (2011). https://doi.org/10.1007/s00542-011-1351-6

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