MEMS and sensors

Which correctly describes deep RIE (the Bosch process) used in MEMS fabrication?

  1. AIsotropic etching with chemical solutions
  2. BAlternating etching with deposition of a sidewall passivation film to form deep, vertical holes and trenches
  3. CPolishing the wafer to thin it
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Answer: B. Alternating etching with deposition of a sidewall passivation film to form deep, vertical holes and trenches

The Bosch process alternates, in short cycles, between etching silicon with SF6 or similar and depositing a passivation film with C4F8 or similar. The sidewalls are protected by the film while only the bottom advances, creating deep, vertical, high-aspect-ratio structures. It is used for MEMS and TSV fabrication.

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