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

article

Parappurath Krishna Menon¹  Avvaru Venkata Narasimha Rao¹  Airpula Linga Murthy¹  Ashok Kumar Pandey²  Prem Pal³ 

[1] Research Centre Imarat;Department of Mechanical and Aerospace Engineering, Indian Institute of Technology;Department of Physics, Indian Institute of Technology

关键词: elemental semiconductors;    oxidation;    masks;    silicon;    encapsulation;    microsensors;    sputter etching;    microfabrication;    potassium hydroxide;    mask layer;    etching characteristics;    oxide layer;    hole etching;    silicon dioxide;    pure KOH solution;    high speed etching;    silicon wafer;    MEMS inertial sensors;    conventional metal etch;    silicon shadow mask;    wafer level encapsulation;    double side wet anisotropic etching;    hydroxylamine;    through hole fabrication;    surface morphology;    temperature 50.0 degC to 60.0 degC;    Si;   

DOI  :  10.1049/mnl.2019.0570

学科分类：计算机科学（综合）

来源: Wiley

【 摘 要 】

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 (NH 2 OH) 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 + NH 2 OH 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.

【 授权许可】

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