In order to enable design of a negative-tone polyphenol resist using polarity-change reaction, five resist
compounds (3M6C-MBSA-BLs) with different number of functional group of &ggr;-hydroxycarboxyl acid were prepared
and evaluated by EB lithography. The resist using mono-protected compound (3M6C-MBSA-BL1a) showed 40-nm hp
resolution at an improved dose of 52 &mgr;C/cm2 probably due to removal of a non-protected polyphenol while the
sensitivity of the resist using a compound of protected ratio of 1.1 on average with distribution of different protected
ratio was 72 &mgr;C/cm2. For evaluation of the di-protected compound based resist, a di-protected polyphenol was
synthesized by a newly developed synthetic route of 3-steps reaction, which is well-suited for mass production. The
resist using di-protected compound (3M6C-MBSA-BL2b) also showed 40-nm hp resolution at a dose of 40 &mgr;C/cm2,
which was faster than that of mono-protected resist. Fundamental EUV lithographic evaluation of the resist using
3M6C-MBSA-BL2b by an EUV open frame exposure tool (EUVES-7000) gave its estimated optimum sensitivity of 7
mJ/cm2 and a proof of fine development behavior without any swelling.
In electron projection lithography (EPL), a proximity-effect was the most significant problem to critical dimension (CD) control. It was remarkable, especially when beam blur was as large as the minimum pattern size. We have developed proximity-effect correction software for EPL to solve this problem. First, this software made a correction table automatically. In this table, the optimum biases were given for various backward-scattering energy levels and beam blurs regarding all kinds of model patterns. Next, every pattern edge was classified in any of the model patterns. Then, the bias for each edge was determined taking certain proportion between the correction table bias and the previous bias. After that, pattern shape was modified. Those processes were iterated until every change in bias was less than 0.5 nm. Finally, stitching pattern features were added. This software was tested using actual 70-nm rule chip data. Errors in energy level for various kinds of patterns were better than 3 percent and line end shortening was successfully corrected. Data size expansion after the correction was about 10 percent. Processing time was about 10 hours on six PCs cluster system. In conclusion, this software provides enough CD uniformity and pattern fidelity for EPL practically. In addition, this software is applicable to not only EPL but also to EB-direct writing.
In electron-beam projection lithography (EPL), the proximity effect is more complicated than in conventional direct electron-beam writing. The correction of this effect uses pattern-shape modification because dose adjustment is not possible. Moreover, large sub-field transcription produces non-uniform beam blur due to optical aberration and local and global Coulomb effects. This large beam blur requires sophisticated correction depending on pattern features and layout over a very short range as well as pattern density over a backscattering range. In response to these issues, the authors have developed a flexible and precise correction method for the proximity effect under various conditions of beam blur, LSI process, and pattern arrangement. It features (1) multiple pattern-area-density maps, (2) look-up tables classified by pattern features and layout, and (3) a fast calculation algorithm for the iteration process of optimal bias. The developed method (running on four PCs with 2.4-GHz CPUs) attains a processing time of 55 min by using a bias map for 12-GB LSI flat data in 2000 sub-fields. An example of pattern classification by this method showed the usefulness of pattern bias for each individual pattern edge over a short range. It is concluded that the developed correction method is useful not only for proximity effects, including the Coulomb effect, but also for various process effects in mask making with precise CD control.