Patent ID: 8148052

Claim:
A method of forming a pattern in at least one device layer in or on a substrate comprising the steps of: a) coating the device layer with a first photoresist layer; b) exposing the first photoresist using a first mask; c) developing the first photoresist layer to form a first pattern on the substrate; d) coating the substrate with a protection layer; e) treating the protection layer to cause a change therein where it is in contact with the first photoresist, to render the changed protection layer substantially immune to a subsequent exposure and/or developing step; f) coating the substrate with a second photoresist layer; g) exposing the second photoresist layer using a second mask; and h) developing the second photoresist layer to form a second pattern on the substrate without significantly affecting the first pattern in the first photoresist layer, i) wherein the first and second patterns together define interspersed features having a spatial frequency greater than that of the features defined in each of the first and second patterns separately.