US Patent 11660722 Polishing system with capacitive shear sensor

A chemical mechanical polishing system includes a platen to support a polishing pad, a carrier head to hold a substrate and bring a lower surface of the substrate into contact with the polishing pad, and an in-situ friction monitoring system including a friction sensor. The friction sensor includes a pad portion having a substrate contacting portion with an upper surface to contact the lower surface of the substrate, and a pair of capacitive sensors positioned below and on opposing sides of the substrate contacting portion.