Patent ID: 7727049

Claim:
An apparatus to monitor a frictional coefficient of a substrate undergoing polishing, comprising: a support to hold a polishing article in contact with a substrate; a member having a surface to contact an exposed surface of the substrate, the member configured to be laterally displaced relative to the polishing article in response to a frictional force from the substrate; a first restorative material configured to apply a force on the member perpendicular to the exposed surface to bias the surface toward the exposed surface, the first restorative material configured to be laterally displaced relative to the polishing article in response to the lateral displacement of the member; a second restorative material configured to move in response to the lateral displacement of the member, the second restorative material configured to apply a lateral force on the member to bias the member toward a neutral lateral position relative to the polishing article; and a sensor mounted on the second restorative material, the sensor configured to generate a signal based on the movement of the second restorative material.