Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110)
- 1.3k Downloads
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.
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.
- Bhat KN, Yellampalle C, DasGupta N, DasGupta A, Rao PRS (2003) Optimization of EDP solutions for feature size independent silicon etching. Proc. SPIE Symposium on Micromachining and Microfabrication 4979:70–78Google Scholar
- Dutta S, Pal R, Kumar P, Hooda OP, Singh J, Shaveta SaxenaG, Datta P, Chatterjee R (2009) Fabrication challenges for realization of wet etching based comb type capacitive microaccelerometer structure. Sens Transducers J 111:18–24Google Scholar
- Lee D, Yu K, Krishnamoorthy U, Solgaard O (2009) Vertical mirror fabrication combining KOH Etch and DRIE of (110) silicon. IEEE J MEMS 18:217–227Google Scholar