CMP and cleaning

Which method is commonly used to count particles on a wafer surface after cleaning?

  1. AWeighing the wafer
  2. BScanning a laser across the wafer surface and detecting light scattered by particles
  3. CBreaking the wafer and examining the cross section
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Answer: B. Scanning a laser across the wafer surface and detecting light scattered by particles

Particle inspection tools (surface inspection systems) scan a laser across a rotating wafer and detect light scattered by particles and defects, determining their positions and sizes. They are often used with unpatterned wafers to evaluate cleaning and tool cleanliness.

  • A. Particles weigh far too little to count by weight.
  • B. Correct. Particles are detected by scattered laser light.
  • C. Cross sections cannot count particles over the whole surface.
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More CMP and cleaning questions

  1. Why is it considered important to transfer wafers to cleaning right after CMP while still wet, without letting them dry?
  2. What is a point of caution for batch cleaning, in which many wafers are immersed in the same tank of cleaning solution?
  3. Which cleaning method, researched and commercialized for removing particles without collapsing fine patterns, sprays tiny particles of cryogenic carbon dioxide or argon?
  4. What is the main purpose of a CMP head that can vary the pressure pressing the wafer in several concentric zones?
  5. Which CMP method fixes the abrasive particles in the polishing pad instead of putting them in the slurry?