Exposure control for phase shifting photolithographic masks

Abstract

Mask and integrated circuit fabrication approaches are described to facilitate use of masks where substantially all of a layout is defined using phase shifting. Exposure settings including relative dosing between the phase shift mask and the trim masks are described. Additionally, single reticle approaches for accommodating both masks are considered. In one embodiment, the phase shifting mask and the trim mask are exposed using the same exposure conditions that have an effect on the characteristics of the radiation used for the exposure, except for relative dosing. The same exposure conditions are changeable optical parameters that consist of numerical aperture (N.A.), wavelength (λ) of radiation, partial coherency (σ), illumination configuration, and defocus. These approaches facilitate better exposure profiles for the resulting ICs and can thus improve chip yield and increase throughput by reducing the need to alter settings and/or switch reticles between exposures.