Slotted retaining ring for polishing head and method of using

A chemical mechanical polishing head comprising:

• a slotted retaining ring constructed by a toroidal ring member having parallelly situated planar top and bottom surfaces, said toroidal ring member further having an inner periphery defined by an inner diameter and an outer periphery defined by an outer diameter, said inner diameter being sufficiently large for holding a polishing head therein, and
• plurality of slot recesses in said bottom surface of said toroidal ring, each of said plurality of slot recesses being formed in a tapered shape having a base portion adjacent to said outer periphery and a tip portion of a smaller width than said base portion adjacent to said inner periphery, and
• a membrane assembly adapted for mounting inside said slotted retaining ring and for carrying a wafer having a surface to be polished therein said bottom surface having a plurality of slot recesses of said slotted retaining ring being substantially in the same plane as said surface of the wafer to be polished.