US Patent 7691549 Multiple exposure lithography technique and method

A method for forming high resolution patterns on a substrate surface is disclosed. A photolithographic patterning tool is loaded with a substrate having a photoimagable layer. Multiple exposures to using interference patterns and developments are performed on the photoimagable layer to define a composite line pattern in the photoimagable layer. The composite line pattern having a greater pitch density than possible with single exposure with the same photolithographic patterning tool. The lines of the composite line pattern are selectively cut or trimmed at a plurality of locations to define a desired pattern in the photoimageable layer. The cuts can themselves be achieved with a plurality of photomasks or exposure to direct write tools to achieve densities beyond that allowed by k1>0.25 limit.