Lithographic photomask alignment using non-planar alignment structures formed on wafer

Abstract

Techniques are provided for fabricating and utilizing optically opaque non-planar alignment structures in non-die areas (e.g., kerf areas) of a wafer to align photomasks to die areas on the wafer. For example, an insulating layer is formed over non-die and die areas of the wafer. A non-planar alignment feature is formed in the insulating layer in the non-die area. An optically opaque layer stack is formed in the die and non-die areas of the wafer, which conformally covers the non-planar alignment feature to form an optically opaque non-planar alignment structure in the non-die area. A lithographic patterning process is performed to pattern the optically opaque layer stack in the die area, wherein the optically opaque non-planar alignment structure in the non-die area is utilized to align a photomask to the die area. The optically opaque non-planar alignment structure can include any type of non-planar structure having a stepped sidewall surface.