Patent ID: 6712673
Filing Date: 2004-03-30
Classification: B24B

Abstract:
A wafer polishing apparatus for polishing a front surface of a wafer, the polishing apparatus comprising:a base for supporting elements of the polishing apparatus; a turntable mounted on the base for rotation about an axis on the base and adapted to support a polishing pad for conjoint rotation with the turntable, the polishing pad having a work surface engageable with the front surface of the wafer for use in polishing the front surface of the wafer; a turntable drive mechanism operatively connected to the turntable for selectively driving rotation of the turntable about the axis of rotation; and a polishing head mounted for holding the wafer in generally opposed relation with the turntable and for rotation about an axis generally parallel to the axis of rotation of the turntable, the polishing head including a back plate having at least a central region in opposed relation with a rear surface of the wafer when the wafer is received by the polishing head, and an annular sealing ring of flexible material having a first surface and second surface opposite said first surface defining a thickness and disposed around the central region of the back plate, the sealing ring having a central opening extending through the complete thickness of the sealing ring, the sealing ring being adapted to flex and conform to the rear surface of the wafer upon receiving the wafer on the polishing head such that a portion of the first surface conforms to a peripheral edge margin of the wafer and a portion of said second surface faces the back plate, wherein the central opening as measured when not engaging the wafer is less than 90% of the wafer diameter so that the first surface conforms to more than 10% of the wafer diameter at the outer peripheral edge margin of the wafer to frictionally engage the wafer, and wherein the rear surface of the wafer, the sealing ring and the back plate define a substantially fluid-tight cavity for controlling fluid pressure in the cavity.