CMP and cleaning
Which method is used to detect the polishing endpoint in CMP?
- AWeighing the wafer after polishing
- BMonitoring changes in friction during polishing (such as motor torque) or in optical reflectance
- CVisually checking the color of the slurry
Show answer and explanation
Answer: B. Monitoring changes in friction during polishing (such as motor torque) or in optical reflectance
When the film being polished is gone and the underlayer is exposed, friction and the surface's optical reflectance change. CMP tools detect the endpoint in real time by monitoring the torque of the motor that turns the platen or the reflection of light shone on the wafer during polishing.