Real-time in-situ microscopic observation of bubbles and roughening in KOH etching of silicon

Alvimar S. Louro; Jose Roberto Senna

doi:10.1117/12.442954

28 September 2001 Real-time in-situ microscopic observation of bubbles and roughening in KOH etching of silicon

Alvimar S. Louro, Jose Roberto Senna

Proceedings Volume 4557, Micromachining and Microfabrication Process Technology VII; (2001) https://doi.org/10.1117/12.442954
Event: Micromachining and Microfabrication, 2001, San Francisco, CA, United States

Abstract

It has been conjectured that the primary cause of roughness of silicon surfaces etched in KOH is random masking of the silicon surface by the H₂ bubbles produced in the reaction. In order to test this model, we have observed and measured bubbles occurring during (100) silicon etching in aqueous KOH solutions. We have confirmed the trends for the average bubble departure radius R_d and average dwell time T_d noted by previous authors under different circumstances: T_d invariably decreases for increasing temperature and concentration and R_d decreases with increasing concentration and flow speed. Two distinct kinds of topography result from the hour long etch. A region that was covered by bubbles looks like a superposition of shallow depressions, with lateral radii comparable to the bubble departure radius and roughness consistent with a pseudo-masking model . Therefore the roughness is dominated by the effect of bubbles and determined by bubble parameters if when and where those do occur. A different roughening regime, resulting in hillocks, is reached by decreasing T_d and bubble density (for instance by increasing flow speed). Depending on the parameters bubbles do not occur over all the surface being etched, or do not occur at all.

Citation Download Citation

Alvimar S. Louro and Jose Roberto Senna "Real-time in-situ microscopic observation of bubbles and roughening in KOH etching of silicon", Proc. SPIE 4557, Micromachining and Microfabrication Process Technology VII, (28 September 2001); https://doi.org/10.1117/12.442954

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