High speed etching of silicon in KOH + NH 2 OH solution at lower temperatures for the fabrication of through holes in silicon wafer

Krishna Menon, Parappurath and Narasimha Rao, Avvaru Venkata and Linga Murthy, Airpula and Pandey, Ashok Kumar and Pal, Prem (2020) High speed etching of silicon in KOH + NH 2 OH solution at lower temperatures for the fabrication of through holes in silicon wafer. Micro & Nano Letters, 15 (6). pp. 365-369. ISSN 1750-0443

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Abstract

In the fabrication of complicated MEMS inertial sensors, there are many instances where metallisation cannot be done by usual methods such as lift off or conventional metal etch. In such cases, a shadow mask needs to be used. A silicon shadow mask can be realised by the fabrication of through holes in silicon. This also can be used as a cover wafer for wafer level encapsulation by fabricating a cavity in the device region. The fabrication of the shadow mask is carried out by doing double side wet anisotropic etching using potassium hydroxide (KOH) + hydroxylamine (NH2OH) solution at low temperatures of 50-60°C. The low temperature of etching is preferred so as to reduce the etching of thermal oxide used as a mask layer. This work focuses on the etching characteristics of the KOH+NH2OH solution at low temperatures in terms of etch rate, undercutting, surface morphology, and selectivity of an oxide layer with silicon. This is very useful in through hole etching using silicon dioxide as a mask. The effect of aging on these characteristics is also studied and this is useful in continuous etching spread over few days especially during pilot production. The results are compared with those obtained using a pure KOH solution.

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IITH Creators:
IITH CreatorsORCiD
Pandey, A.K.UNSPECIFIED
Pal, P.UNSPECIFIED
Item Type: Article
Uncontrolled Keywords: Conventional metals; Etching characteristics; Low temperatures; Lower temperatures; MEMS inertial sensors; Pilot production; Wafer-level encapsulation; Wet anisotropic etching;Amines; Anisotropic etching; Fabrication; Morphology; Pilot plants; Potassium hydroxide; Silica; Silicon wafers; Surface morphology; Temperature
Subjects: Physics
Divisions: Department of Physics
Depositing User: . LibTrainee 2021
Date Deposited: 19 Jul 2021 04:51
Last Modified: 19 Jul 2021 04:51
URI: http://raiith.iith.ac.in/id/eprint/8409
Publisher URL: http://doi.org/10.1049/mnl.2019.0570
OA policy: https://v2.sherpa.ac.uk/id/publication/13658
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