CMP and cleaning
When removing particles from a wafer surface by cleaning, how does particle size generally relate to ease of removal?
- AThe smaller the particle, the stronger its adhesion relative to its weight and the forces from flow, so it is harder to remove
- BParticle size does not matter
- CSmaller particles are easier to remove
Show answer and explanation
Answer: A. The smaller the particle, the stronger its adhesion relative to its weight and the forces from flow, so it is harder to remove
Adhesion forces such as van der Waals forces that hold particles to a surface scale roughly with particle size, while forces from liquid flow or ultrasound shrink with the square or cube of size. Smaller particles are therefore harder to remove, and cleaning has grown more difficult with scaling.
- A. Correct. Adhesion becomes relatively stronger for smaller particles.
- B. Particle size strongly affects ease of removal.
- C. Smaller particles are harder to remove.