Wafer carrier head with inflatable bladder and attack angle control for

Abstract

A carrier head that holds an object such as a wafer for a polishing system can be rotated during polishing. One such carrier head includes a sensor that determines the relative orientation of (or the angle between) a movable chuck and a fixed drive structure. A control system uses these measurements to select the edge pressure applied to the wafer or the chuck to control the attack angle of the wafer against polishing pads. By actively adjusting the attack angle, a carrier head can accommodate torques about an axis not in the plane of contact between the wafer and the polishing pad even when the wafer is otherwise free to rotate about the axis. One carrier head includes a drive plate with projections ending with balls that are disposed in matching openings in a carrier plate. Radial elongation of openings and curvature of the balls permit rotation of the carrier plate about an axis in plane passing between the carrier and drive plates. Another aspect of the invention provides a flexible bladder connected to a conduit formed in a drive shaft of the carrier head. A wafer is mounted adjacent the bladder so that pressure from the conduit causes the bladder to expand and apply a uniform pressure to the wafer for polishing.