A completely new concept for designing the illumination aperture filter is suggested. From experimental or simulative methods, we have extracted the performance of every individual beam component on the illumination plane. The optimal apertures are then obtained by superimposing the best components that meet the requirements demanded by the specific photo processes. Different kinds of optimal apertures were successfully implanted to deal with different process problems. Therefore, it is called the customized illumination aperture filter (CIF). The zero 1D OPE CIF, as a proof of concept, was designed to eliminate the OPE of low k process. Without any OPC, O.6.tm DOF ofthe common ED window was obtained, where ki 0.39 for our NA0.55 stepper to print 0. 18.tm line patterns. To push to smaller ki, another CIF was designed to maximize the individual DOF and overcome the reduced power problem accompanied with the typical aggressive OAI.Using this CIF, we achieved I . Im common DOF with 7% EL for 0. 1 8.tm line patterns. The CIF doubles the power of the Nikon's strong quadrupole, shrinc. An ultimate resolution limit of 0. 1 1.tm line pattern was reached as well with the CIF. Finally, a contact/via CIF was designed combined with a half-tone PSM (6%). The CIF gives about O.8im common DOF with 7% EL for O.2.tm holes and O.7.tm DOF for 0. l7prn holes using thinner resist. The CIF approach is, therefore, proven to be a cost effective and relatively easy realizable alternative to the alternating PSM for extremely low ki process applications.
A theoretical analysis to estimate the effect of shot noise on CDU is induced from optical imaging perspectives combined with quantum theory, and is studied for 193-nm, EUV, and electron beam lithography. We found the CDU variation from shot noise is related to the number of particles absorbed in the printed area and to the image log slope (ILS). Hence, the CDU variation contributed by shot noise gets worse when the technology node advances from 45-to 32-, 22-, and 15-nm, EUV with higher ILS is no exception. For e-beam lithography, we are interested in the values of ILS calculated from array structures with different pitches, backscattering, wafer-stage movement, and raster-scan writing.
ArF immersion lithography is essential to extend optical lithography. In this study, we characterized the immersion process on production wafers. Key lithographic manufacturing parameters, overlay, CD uniformity, depth of focus (DOF), optical proximity effects (OPE), and defects are reported. Similar device electrical performance between the immersion and the dry wafers assures electrical compatibility with immersion lithography. The yield results on 90-nm Static Random Access Memory (SRAM) chips confirm doubling of DOF by immersion as expected. Poly images of the 65-nm node from a 0.85NA immersion scanner are also shown.
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