Deposition (CVD and PVD)

What is the purpose of placing a plate with many holes (a collimator) between the target and wafer in a sputtering system?

  1. ATo block atoms flying at oblique angles and pass only near-vertical ones, making it easier to coat the bottoms of holes
  2. BTo increase the deposition rate
  3. CTo cool the wafer
Show answer and explanation

Answer: A. To block atoms flying at oblique angles and pass only near-vertical ones, making it easier to coat the bottoms of holes

A collimator is a honeycomb-like plate that blocks sputtered atoms arriving at oblique angles and passes only those heading nearly perpendicular to the wafer. This improves coverage at the bottom of deep holes (bottom coverage). However, film also deposits on the collimator, so the deposition rate drops.

  • A. Correct. It passes only near-vertical atoms.
  • B. It blocks some atoms, so the rate actually drops.
  • C. Cooling the wafer is not the purpose.
Practice this topic Back to topic

More Deposition (CVD and PVD) questions

  1. In PVD such as sputtering and evaporation, why is it hard to coat the sidewalls and bottoms of deep trenches?
  2. What is it called when a gas containing a dopant such as phosphorus is flowed during LPCVD polysilicon deposition to make a conductive film?
  3. Before filling contact holes with tungsten by CVD, what is the main reason a thin film such as TiN (titanium nitride) is deposited underneath?
  4. What is the main purpose of "densification", a high-temperature anneal after depositing oxide by low-temperature CVD or similar?
  5. In ALD, what is the temperature range called in which self-limiting surface reactions keep the thickness per cycle constant?