Patent ID: 6623343
Filing Date: 2003-09-23
Classification: B24B

Abstract:
A polishing head for positioning a substrate having a surface on a polishing pad of a polishing apparatus, the polishing head comprising:a subcarrier plate having an outer surface; an annular first membrane coupled to the subcarrier plate, the first membrane having a receiving surface adapted to receive the substrate thereon, and a lip adapted to seal with a backside of the substrate to define a first chamber between the backside of the substrate and the outer surface of the subcarrier plate; a second membrane positioned above the first membrane, the second membrane coupled to the subcarrier plate to define a second chamber between an inner surface of the second membrane and the outer surface of the subcarrier plate, the second membrane comprising a skirt portion having a first hardness and a lower surface portion having a second hardness; wherein during a polishing operation pressurized fluid introduced into the second chamber causes it to expand outward to exert a force on a portion of the backside of the substrate, thereby pressing a predetermined area of the surface of the substrate against the polishing pad; and wherein a pressurized fluid at a lower pressure than that introduced into the second chamber is introduced into the first chamber to directly press the surface of the substrate against the polishing pad.