CMP and cleaning

In processes such as multilevel wiring, what is the main reason the wafer surface must be planarized by CMP?

  1. ATo polish the surface for appearance
  2. BBecause remaining unevenness causes areas to be out of focus in the next exposure and makes film processing difficult
  3. CTo make the wafer heavier
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Answer: B. Because remaining unevenness causes areas to be out of focus in the next exposure and makes film processing difficult

Each added layer increases surface unevenness, and once it exceeds the range the exposure tool can keep in focus (depth of focus), patterns can no longer be transferred accurately. Steps also make film deposition and processing harder. Planarizing with CMP made it possible to stack many wiring layers.

  • A. It is not a step for appearance.
  • B. Correct. Planarization is needed for exposure and processing.
  • C. It is not meant to make the wafer heavier.
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More CMP and cleaning questions

  1. Which correctly describes the basic configuration of a CMP tool?
  2. In Cu interconnect CMP, why is polishing generally divided into stages?
  3. Which correctly describes the general difference between hard and soft CMP polishing pads?
  4. What is the state of a silicon surface whose last cleaning step was dilute hydrofluoric acid?
  5. What is the main purpose of installing filters in the lines that supply CMP slurry to the polisher?