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 "1 00% transmission PSM", has been used to demonstrate the potential for achieving quarter-wavelength optical lithography (k1' 0.2). The ability to print 7Onm lines through pitch using a 248nm, O.7ONA wafer scanner, QUASAR off axis illumination, and a chromeless mask (CLM) has been demonstrated.' However, it was confirmed by Chen, et al., that imaging complex 2D 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 2D structures is decreased. The nature of the proximity effects observed with chromeless phase lithography and the means to correct for them using various optical proximity correction (OPC) methods are described and explained. Patterns representing real device-like structures are used to demonstrate that data processing algorithms are feasible which can correct for the induced proximity effects and thus make it possible to incorporate CPL technology for low-k, production lithography.Chromeless phase lithography (CPL) is a recent development in the arena of phase shifting masks that is showing enormous potential for being a manufacturable solution for low k, imaging. There are several benefits to using this approach, which is essentially a 1 00% transmission attenuated phase shifting mask. Because the image enhancement results from making areas of the drawn geometries transparent with a phase shift of 1 80 degrees as opposed to alternating the phase between 0 and 1 80 degrees on either side of drawn opaque geometries (as in alternating PSM), there is no requirement for phase assignment. As a consequence, there are no phase conflicts that must be resolved by either redefming the zero and 1 80 degree phase regions or by placing design restrictions on the layout, which makes the data conversion much simpler. This also means there are no unwanted phase edges that must be removed by a second exposure using a trim mask, making CPL a single-mask, single-exposure solution to low k, manufacturing. Figure 1 illustrates imaging a line/space pattern using the three PSM techniques that utilize etched quartz as a phase shifter; chromeless phase edge, alternating aperture PSM, and CPL. All three techniques have the resolution enhancement of 2 beam imaging, the first two as a result of the alternating 0 and 1 80 degree phase apertures and CPL as a result of off-axis illumination. Finally, CPL is not a single layer technology that can only be applied to the poly gate layer. Because this technique has the potential to be applied to a large range of pattern types (including poly gate, contact, via, local...