CMP and cleaning

What is the main cause of pattern collapse when cleaning and drying high-aspect-ratio patterns?

  1. AGravity acting on the patterns
  2. BSurface tension of liquid remaining between the patterns as it dries
  3. CThe color of the cleaning solution
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Answer: B. Surface tension of liquid remaining between the patterns as it dries

If liquid remains between tall, narrow patterns as they dry, surface tension at the liquid surface pulls the patterns together, causing them to collapse or stick. Countermeasures include replacing the liquid with one of lower surface tension, making the surface hydrophobic, and supercritical drying.

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More CMP and cleaning questions

  1. Why are oxidizers such as hydrogen peroxide added to the slurry in tungsten CMP?
  2. What is a correct design countermeasure to the CMP removal amount varying with pattern density within a chip?
  3. What is the approximate size of the abrasive particles in CMP slurries?
  4. What is the main purpose of diluting chemicals or using functional water in recent cleaning processes?
  5. What is the main purpose of cleaning the back and edge (bevel) of wafers?