Patent ID: 7892070

Claim:
A process of polishing comprising: providing a polishing apparatus comprising: a platen having a platen surface lying along a first plane; a platen window having a window surface lying along a second plane different from the first plane; and a polishing pad attached to the platen surface and including: a first layer including a first polishing surface and a first opening, wherein the first opening extends through the first layer and has a first perimeter; a second layer distinct from and adjacent to the first layer, wherein the second layer comprises a second opening extending through the second layer and having a second perimeter different from the first perimeter of the first opening; and a pad window lying within the first opening of the first layer and the second opening of the second layer, and abutting the window surface of the platen window; wherein the platen window extends into the second opening but not into the first opening; applying a fluid to the polishing pad; placing a workpiece adjacent to the polishing pad; compressing the polishing pad between the workpiece and the platen; and polishing the workpiece such that the pad window contacts the workpiece.