Detecting the endpoint of chem-mech polishing, and resulting semiconductor device

Abstract

A contact structure is formed atop a semiconductor wafer at a level whereat it is desired to terminate polishing of a layer overlying the contact structure. When the contact structure becomes exposed to a polishing slurry, an electrical characteristic, such as resistance or impedance, is registered by measuring apparatus. In one embodiment, two or more contact structures are formed atop the wafer, vias are formed through the wafer, and the vias are filled, thereby providing a conductive path from the contact structures to the back side of the wafer. The measuring apparatus probes the filled vias on the back side of the wafer. A change in resistance/impedance indicates that the contact structures have become exposed during polishing, and polishing is terminated. In another embodiment of the invention, one or more contact structures are formed atop the wafer. The measuring apparatus is connected to a probe in the polishing slurry, and to the wafer itself, such as to the back side of the wafer. Again, a change in resistance/impedance indicates that the contact structures have become exposed during polishing, and polishing is terminated.

Dependencies are inferred from the claim text.