Combined TMAH and HF sacrificial layer etching technique for surface micromachined devices

Thomas Lisec; Martin Kreutzer; Beatrice Wenk; Bernd Wagner

doi:10.1117/12.221285

19 September 1995 Combined TMAH and HF sacrificial layer etching technique for surface micromachined devices

Thomas Lisec, Martin Kreutzer, Beatrice Wenk, Bernd Wagner

Proceedings Volume 2639, Micromachining and Microfabrication Process Technology; (1995) https://doi.org/10.1117/12.221285
Event: Micromachining and Microfabrication, 1995, Austin, TX, United States

Abstract

This paper presents a two step sacrifical layer etching technique used for the fabrication of surface mciromachined piezoresistive pressure sensors. The sacrificial layer itself is a sandwich structure of a thin polysilicon layer with the underetching channels and a much thicker 'buried' oxide underneath. First the polysilicon part is etched in an aqueous TMAH solution with high etch rates realizing a first shallow cavity. After rinsing, the oxide part is removed in 7:1 buffered HF. Since the oxide is etched now vertically, the process is completed within minutes. Sticking is suppressed successfully and non special drying techniques are required. The whole sensor structures could be passivated by LPCVD or PECVD layers against both etchants. Although the final depth of the cavity is 1 micrometers the sensor structure remains nearly flat. This minimizes technological problems concerning for example the piezoresistor definition or the sealing of the sensor and reduces the noise in the piezoresistor arrangement.

Citation Download Citation

Thomas Lisec, Martin Kreutzer, Beatrice Wenk, and Bernd Wagner "Combined TMAH and HF sacrificial layer etching technique for surface micromachined devices", Proc. SPIE 2639, Micromachining and Microfabrication Process Technology, (19 September 1995); https://doi.org/10.1117/12.221285

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