Deposition (CVD and PVD)

When filling a narrow trench by deposition, what problem tends to occur if film builds up thickly near the trench opening (overhang)?

  1. AThe trench gets overfilled with film
  2. BThe film becomes a conductor
  3. CThe opening closes first, leaving a void inside the trench
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Answer: C. The opening closes first, leaving a void inside the trench

If film builds up thickly at the corners of the trench opening, the opening closes before enough film coats the bottom and sidewalls, leaving a void inside. Voids cause open circuits and reduced reliability, so countermeasures include choosing the deposition method and combining deposition with etching.

  • A. The opening closes, so the inside is actually underfilled.
  • B. The film's electrical nature does not change.
  • C. Correct. The opening closes and a void remains.
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More Deposition (CVD and PVD) questions

  1. What is the purpose of placing a plate with many holes (a collimator) between the target and wafer in a sputtering system?
  2. In PVD such as sputtering and evaporation, why is it hard to coat the sidewalls and bottoms of deep trenches?
  3. What is it called when a gas containing a dopant such as phosphorus is flowed during LPCVD polysilicon deposition to make a conductive film?
  4. Before filling contact holes with tungsten by CVD, what is the main reason a thin film such as TiN (titanium nitride) is deposited underneath?
  5. What is the main purpose of "densification", a high-temperature anneal after depositing oxide by low-temperature CVD or similar?