Etching

Which are examples of profile defects seen in high-aspect-ratio etching?

  1. ABowing, where the hole widens partway down, and twisting, where the hole bends
  2. BDishing, where wiring becomes dish-shaped in CMP
  3. CShadowing, where tilted implants create shadows
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Answer: A. Bowing, where the hole widens partway down, and twisting, where the hole bends

In deep-hole etching, ions striking the sidewalls can widen the hole partway down (bowing), and charging and other effects can bend or twist holes (twisting). Suppressing these is a major challenge in etching 3D NAND memory holes and similar structures.

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More Etching questions

  1. If the oxide etch rate is 100 nm/min and the mask is consumed at 20 nm/min, what is the selectivity to the mask?
  2. Which solution, made by buffering hydrofluoric acid with ammonium fluoride, is used for wet etching of SiO2?
  3. Why is cryogenic etching, which cools the wafer to very low temperatures, attracting attention for high-aspect-ratio processing?
  4. 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?
  5. What is an advantage of pulsed plasma, which etches while switching the RF power on and off?