Optimization of TMAH etching for MEMS

Sebastiano Brida; Lorenza Ferrario; Vittorio Guarnieri; Flavio Giacomozzi; Benno Margesin; Makarand Paranjape; Giovanni Verzellesi; Mario Zen

doi:10.1117/12.341165

10 March 1999 Optimization of TMAH etching for MEMS

Sebastiano Brida, Lorenza Ferrario, Vittorio Guarnieri, Flavio Giacomozzi, Benno Margesin, Makarand Paranjape, Giovanni Verzellesi, Mario Zen

Author Affiliations +

Proceedings Volume 3680, Design, Test, and Microfabrication of MEMS and MOEMS; (1999) https://doi.org/10.1117/12.341165
Event: Design, Test, and Microfabrication of MEMS/MOEMS, 1999, Paris, France

Abstract

Tetra-methyl ammonium hydroxide (TMAH) is an anisotropic silicon etchant that is gaining considerable use in silicon sensor micromachining due to its excellent compatibility with CMOS processing, selectivity, anisotropy and relatively low toxicity, as compared to the more used KOH and EDP etchants. In this paper, the influence of temperature and concentration of the TMAH solution together with oxidizer additions is studied in order to optimize the anisotropic silicon etching for MEMS fabrication. In particular this optimized etchant formulation has been employed at ITC-Irst in the development of a basic fabrication process for piezoresistive pressure sensors based on a silicon membrane and four resistors connected in a Weatherstone bridge configuration. The active element of the sensor, i.e. the thin silicon membrane, is formed by etching anisotropically from the backside of the wafer. Both process and etching have to be tuned and matched in order to obtain an optimum fabrication sequence. Some improvements such as higher etch rate and better surface finish have been obtained by the addition of ammonium peroxidsulfate as oxidizing agent under different conditions. This simplifies both the post processing and the tech set-up. The process parameters and the thermo-electro-mechanical characteristics of the pressure sensors were tested and are compared with the analytical and numerical simulations.

Citation Download Citation

Sebastiano Brida, Lorenza Ferrario, Vittorio Guarnieri, Flavio Giacomozzi, Benno Margesin, Makarand Paranjape, Giovanni Verzellesi, and Mario Zen "Optimization of TMAH etching for MEMS", Proc. SPIE 3680, Design, Test, and Microfabrication of MEMS and MOEMS, (10 March 1999); https://doi.org/10.1117/12.341165

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