Etching

Which is a characteristic of wet etching of silicon with potassium hydroxide (KOH) solution?

  1. AEtch rates differ greatly between crystal planes, and the (111) plane etches very slowly, producing features such as V-shaped grooves with sloped walls
  2. BIt is isotropic etching that proceeds at the same rate on all crystal planes
  3. CIt dissolves oxide quickly
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Answer: A. Etch rates differ greatly between crystal planes, and the (111) plane etches very slowly, producing features such as V-shaped grooves with sloped walls

Alkaline solutions such as KOH barely etch silicon's (111) planes, so on (100) wafers they produce V-grooves and pyramidal pits with walls sloped at about 54.7°. This anisotropy is used to make MEMS structures and the like.

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More Etching questions

  1. Which is a characteristic of inductively coupled plasma (ICP) etching equipment?
  2. Which metric indicates how small the variation in etch rate is across the wafer?
  3. After the etch endpoint is detected, what is it called to continue etching for a set time to ensure the film is removed across the whole wafer?
  4. What is a mask of nitride, carbon or similar material called, used when photoresist alone cannot survive as a mask, such as when etching deep holes?
  5. Which is a characteristic of downstream etching, which supplies only plasma-generated radicals to the wafer?