US Patent 7901852 Metrology of bilayer photoresist processes

A method for patterning a substrate is provided, which comprises (a) providing a substrate; (b) applying a first layer comprising a first photo resist to the substrate; (c) applying a second layer comprising a second photo resist over the first layer; (d) patterning the second layer; and (e) inspecting the patterned second layer with an inspection tool; wherein at least one of the first and second layers comprises a contrasting agent which increases the contrast between the first and second layers to the inspection tool.