US Patent 9372406 Film portion at wafer edge

A film layer on a substrate of the wafer is patterned to form a first plurality of areas of the film layer and a second plurality of areas of the film layer. The first plurality of areas of the film layer is removed. The second plurality of areas of the film layer is kept on the substrate. A first portion of the film layer is kept on the substrate. A first edge of the first portion of the film layer is substantially near an edge of the wafer. The first portion of the film layer defines a boundary for the wafer.