HTPSM (High-Transmission Phase Shift Mask) is one of the most promising mask technologies for photolithography
resolution enhancement. However, it s well known that the use of HTPSM frequently results in unwanted patterns due to
inevitable pinching effects, particularly in spacious areas. Although pinching effect can be effectively suppressed by the
application of additional Cr patterns at the problematic locations, it is a critical challenge to systematically detect and
automatically correct the complicated patterns in most of realistic cases.
We demonstrated remarkable photolithography process window improvement by the use of HTPSM (A type and
above) with the focus on the development of a systematic methodology for automatic detection and correction of abnormal
patterns due to optical pinching effect. Regular optical rules check (ORC) with specific modifications was employed to
precisely locate the potential pinched areas, whereas enhanced design rules check (DRC) was applied subsequently to
generate the required additional Cr patterns for final mask fabrication. A variety of photolithography variables, such as
wavelength and numerical aperture (NA) were extensively investigated against optical pinching effect to confirm the
feasibility and accuracy of the proposed detection/correction methodology for HTPSM application.
High-transmittance phase shift mask (HTPSM) and high numerical aperture (NA) imaging with polarized illumination have been proposed as one of the solutions of the 65nm technology node and beyond. Both aerial image simulations and experimental exposure results confirm the advantages of the polarized illumination for high NA imaging. However, influence of transmission rate of the PSM status upon imaging performance had not yet been fully investigated. Consequently, the influence of different transmission rate PSM with polarized illumination upon imaging performance including depth of focus (DOF), exposure latitude (EL) and line edge roughness (LER) has been researched in this study. Simulation of normalized intensity log slope (NILS) vs. mask transmission rate for the through pitch line space patterns compared with experimental data are clearly showed. Masks of various transmission rates from 6%~30% have been designed. The print images had been investigated with and without polarized illuminations of 193nm high NA tool. According to the experimental and simulation results, the high transmission rate 15% PSM certainly could enhance resolution for 50nm node and beyond.
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