Fostered by continued advancements in the field of optical extension technologies, optical lithography continues to extend far beyond what was thought possible only a few years ago. The application of chromeless phase lithography (CPL), or ''100% transmission PSM,'' has been used to demonstrate the potential for optical lithography to image features as small as one-quarter of the exposure wavelength at pitches that are below the exposure wavelength. The ability to print 70 nm lines through pitch using a 248 nm, 0.70 numerical aperture (NA) wafer scanner, QUASAR off-axis illumination, and a chromeless mask (CLM) has been demonstrated by Chen et al. [Chen et al., Proc. SPIE. 4346, 515-533 (2001)]. However, it was confirmed by Chen et al. that imaging complex two-dimensional (2-D) structures with high transmission CLM reticles involves very strong optical proximity effects. The need to use high NA wafer steppers with off-axis illumination in order to apply chromeless phase lithography exacerbates these effects. This phenomenon is further magnified and the interactions become more complex as the pitch between 2-D structures is decreased. The nature of the proximity effects observed with chromeless phase lithography and the means by which to correct for them using various optical proximity correction (OPC) methods are described and explained. Patterns that represent real device-like structures are used to demonstrate that data processing algorithms are feasible and can correct the induced proximity effects and thus make it possible to incorporate CPL technology for low-k 1 production lithography.