Polishing head assembly having recess and cap

A polishing head assembly for polishing of semiconductor wafers, the polishing head assembly comprising:

• a polishing head having a top portion and a downwardly extending annular member defining a recess along a bottom portion, the recess having a recessed surface, and holes extending from the top portion through the recessed surface;
• a cap positioned within the recess, the cap having an annular wall extending between and upper surface and a floor extending across the annular wall, the floor being spaced from the recessed surface to form a chamber therebetween, wherein the annular wall has a first portion and a second portion, the first portion having apertures corresponding to the holes, the second portion extending downward from the first portion, and wherein the cap is made of a metallic material, wherein the thickness of the annular wall adjacent the upper surface is greater than a thickness of the annular wall adjacent the floor;
• and
• a unitary one-piece band circumscribing the second portion of the annular wall, wherein the band is made of a non-metallic material;
• wherein the annular member circumscribes a second portion of the annular wall;
• wherein the holes and the corresponding apertures receive fasteners to removably secure the first portion of the annular wall of the cap to the recessed surface of the polishing head;
• and
• wherein the first portion of the annular wall has a first o-ring forming a seal when the first portion and the recessed surface are secured.