Deposition (CVD and PVD)

Which is a characteristic of ALD (atomic layer deposition)?

  1. AIt can deposit films several µm thick quickly in a single step
  2. BIt repeats self-limiting surface reactions of precursors, controlling thickness at the atomic-layer level
  3. CIt is a printing technique that needs no vacuum
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Answer: B. It repeats self-limiting surface reactions of precursors, controlling thickness at the atomic-layer level

ALD repeats a cycle in which a source gas is supplied so that one layer adsorbs on the surface, the chamber is purged, and a reactant gas is supplied to react. Because the surface reaction stops after one layer (self-limiting), thickness can be controlled precisely and films can be deposited uniformly even inside deep trenches. In return, deposition is slow.

One ALD (atomic layer deposition) cycle Precursor A Self-limiting Purge Remove excess A Precursor B Forms one layer Purge Remove byproducts Repeat About 0.1 nm per cycle; thickness is set atom layer by atom layer
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More Deposition (CVD and PVD) questions

  1. What is the main advantage of plasma CVD (PECVD)?
  2. Which correctly describes step coverage in deposition?
  3. Which deposition method is mainly used to fill trenches for copper wiring?
  4. Which is a characteristic of low-pressure CVD (LPCVD)?
  5. Which source gas is commonly used to deposit polysilicon by LPCVD?