Methods of modifying masking reticles to remove forbidden pitch regions thereof

A method is provided, in which a masking reticle including a plurality of pattern blocks is modified, the modifying including: identifying a first pattern block and a second pattern block of the plurality of pattern blocks where at least a first portion of the first pattern block and a second portion of the second pattern block are in parallel relation; and reducing a length of the first portion of the first pattern block when a transverse separation S between corresponding length edges of the first portion of the first pattern block the second portion of the second pattern block falls within a pre-defined forbidden pitch range for the masking reticle. The method may include repeating the identifying and reducing of pairs of pattern blocks on the mask reticle to remove portions of pattern block pairs spaced apart by a transverse separation falling within a forbidden-pitch range.