Patent ID: 7475380

Claim:
A method of generating patterns of a paired set of photomasks from a data set defining a circuit layout to be provided on a substrate, comprising using a processor to perform steps of: a) inputting a circuit layout; b) identifying critical segments of said circuit layout; c) based on said identified critical segments, generating and legalizing block mask patterns for inclusion in a block mask; d) thereafter, based on said identified critical segments and said block mask patterns, generating, legalizing and coloring phase mask patterns to define a phase shift mask for use in a dual exposure method with said block mask for patterning said identified critical segments of said circuit layout; c) and then checking for violation of mask design rules by said mask patterns: f) if there is a violation of said mask design rules, modifying said circuit layout and performing, in order, a step of identifying in critical segments of said modified circuit layout and steps (c) through (e) with respect to said identified critical segments of said modified circuit layout; and g) thereafter, generating data representing said legalized block mask patterns and said colored legalized phase mask patterns, and using said generated data to fabricate said block mask and said phase shift mask, respectively.