Etching

Why is cryogenic etching, which cools the wafer to very low temperatures, attracting attention for high-aspect-ratio processing?

  1. ABecause the etch rate becomes zero
  2. BBecause reactions on the sidewalls are suppressed, making fast, vertical deep etching easier
  3. CBecause plasma is no longer needed
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Answer: B. Because reactions on the sidewalls are suppressed, making fast, vertical deep etching easier

When the wafer is cooled cryogenically, spontaneous chemical reactions by radicals on the sidewalls are suppressed or passivation forms more easily, while etching proceeds at the bottom where ions strike. Deep, vertical holes can therefore be etched quickly, attracting attention for 3D NAND memory-hole etching and similar uses.

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More Etching questions

  1. Because changes in the condition of an etch chamber's walls alter results, what is it called to process dummy wafers before product to stabilize the chamber?
  2. What is an advantage of pulsed plasma, which etches while switching the RF power on and off?
  3. Which gases are commonly used for dry etching of GaN?
  4. Why is it difficult to pattern copper wiring directly by dry etching?
  5. In gate etching, what is the phenomenon called in which the pattern sidewall is undercut laterally near the boundary with the underlying insulator?