Patent ID: 7512928

Claim:
A method of making a mask design having optical proximity correction features, comprising: obtaining a target pattern comprising a plurality of target pattern features corresponding to a plurality of features to be imaged on a substrate; generating a mask design comprising mask features corresponding to the plurality of features to be imaged on the substrate, wherein a first and a second mask feature of the mask features are spaced along a first direction by a pitch (P x1 ) and the second mask feature is spaced from a third mask feature of the mask features along the first direction by a pitch (P x2 ); determining a relationship between (i) a pitch of the first and second mask features and the second and third mask features, and (ii) a spacing of sub-resolution assist features from their corresponding first and third mask features, wherein the relationship provides an indication of an aspect ratio of at least one of the features to be imaged on the substrate corresponding to one of the first and third mask features; and controlling the aspect ratio of the at least one of the features to be imaged on the substrate by positioning one of the sub-resolution assist features proximate to the corresponding mask feature, wherein the sub-resolution assist feature corresponding to the first mask feature is spaced from the first mask feature by a distance (x 1 ), wherein (x 1 ) is determined based on (P x1 ), and wherein the sub-resolution assist feature corresponding to the third mask feature is spaced from the third mask feature by a distance (x 2 ), such that (x 2 ) approximately equals (x 1 ) when (P x2 ) approximately equals (P x1 ), and (x 2 ) is different from (x 1 ) when (P x2 ) is different from (P x1 ).