Reticle critical dimension latitude for fabrication of 0.18 mu m line patterns

The reticle critical dimension (CD) latitude of 0.18 mu m line patterns wit h various pitches was investigated from the standpoint of mask linearity, o ptical proximity effect (OPE) and depth of focus (DOF). We propose a global reticle CD latitude which is defined by the common range of allowable reti cle CDs for various pitches. The global reticle CD latitude was enhanced un der illumination conditions in which the OPE was suppressed, e.g., conventi onal illumination and at the optimum numerical aperture (NA) which gave a w ider DOF, especially for isolated lines. We found experimentally that the g lobal reticle CD latitude (on x4 reticle, range) of 0.18 mu m line patterns was 20 nm at NA = 0.60 and sigma = 0.75 conventional illumination. Further more, from aerial image simulation results, the global reticle CD latitude was expected to be enhanced at the optimum NA (similar to 0.68) by KrF, and at 0.60 NA by ArF lithography.