MONITORING THICKNESS IN FACE-UP POLISHING WITH ROLLER

A chemical mechanical polishing system includes a support configured to hold a substrate face-up, a polishing article having a polishing surface smaller than an exposed surface of the substrate, a port for dispensing a polishing liquid, one or more actuators to bring the polishing surface into contact with a first portion of the exposed surface of the substrate and to generate relative motion between the substrate and the polishing pad and optically transmissive polymer window, an in-situ optical monitoring system, and a controller configured to receive a signal from the optical in-situ monitoring system and to modifying a polishing parameter based on the signal. The optical monitoring system includes a light source and a detector, the in-situ optical monitoring system configured to direct a light beam from above the support to impinge a non-overlapping second portion of the exposed surface of the substrate.