Chipmaking is an amazing thing. I’m constantly impressed by our industry’s ability to fabricate trillions of nanoscale features on a single silicon wafer with such precision and repeatability. Some of the processes we use seem suitably high-tech, employing lasers, electron beams and depositing films atom by atom. Then, on the other hand, there are processes that are, at least in principle, positively primitive in comparison.At various points in making a microchip, the surface of the wafer has to be made perfectly flat, or planarized. This is done either to remove excess material, or to create a perfectly flat foundation for adding the next layer of circuit features. To do this, chipmakers use a process called chemical-mechanical planarization, or CMP, for short. CMP involves pouring a mixture of chemicals and sand (more-or-less) on a spinning disc of special sandpaper and polishing away.Let’s remember here that semiconductor fabs go to great lengths to keep wafers free of contaminants. Clean rooms have elaborate filtration systems to keep the air purity a million times higher than outside and workers are enveloped in bunny suits and masks to trap organic debris.So, on the face of it, CMP seems to be a very odd thing to do in a clean room.