Etching

What is the masking scheme called that stacks three layers, an organic (carbon) film at the bottom, a silicon-containing middle layer and resist on top, to etch fine patterns deeply?

  1. ATrilayer resist process
  2. BDamascene process
  3. CLOCOS process
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Answer: A. Trilayer resist process

In the trilayer process, the thin resist pattern is first transferred into the silicon-containing middle layer, which then serves as the mask for etching the thick organic film with oxygen-based plasma. Chaining the high selectivities of different materials in sequence produces a thick, robust mask from thin resist.

  • A. Correct. Three layers are stacked and the pattern is transferred in sequence.
  • B. Damascene forms wiring by filling trenches with metal.
  • C. LOCOS is isolation by selective oxidation.
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More Etching questions

  1. Which gas can etch silicon isotropically without a plasma, for example to remove sacrificial layers in MEMS?
  2. Which technique gradually thins an exposed resist pattern with plasma to create lines narrower than the exposure limit?
  3. In gate electrode etching, what is commonly done to preserve the thin gate insulator underneath?
  4. When a 1 µm film is etched just down to the underlayer by perfectly isotropic wet etching, roughly how much is etched laterally from the mask edge (undercut)?
  5. Which metric expresses how far the sidewall of an etched hole or trench tilts from vertical?