CMP and cleaning

In SC-1 (a mixture of ammonia and hydrogen peroxide), what role does the hydrogen peroxide play?

  1. AIt glues particles to the surface
  2. BIt hydrogen-terminates the surface
  3. CIt oxidizes the silicon surface to cover it with a thin oxide, preventing direct roughening by ammonia while the surface continues to be etched slightly
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Answer: C. It oxidizes the silicon surface to cover it with a thin oxide, preventing direct roughening by ammonia while the surface continues to be etched slightly

In SC-1, hydrogen peroxide oxidizes the silicon surface to form a thin oxide, and ammonia slowly dissolves that oxide. With oxidation and etching proceeding together, the surface is removed little by little, lifting particles off for removal. If there is too little peroxide, ammonia etches the silicon directly and roughens the surface.

  • A. The solution is for removing particles.
  • B. Hydrogen termination results from dilute HF treatment.
  • C. Correct. It oxidizes and protects the surface while slight etching continues.
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More CMP and cleaning questions

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