The authors proposed a newly three-dimensional isolation system, consisting of a rubber bearing, vertical oil dampers and disc spring units, to reduce the seismic response in the vertical direction as well as horizontal direction. This isolation system is employed with a number of disc spring units to provide the vertical restoring force to the superstructure. The disc spring units are combined by three disc springs in parallels and they are are stacked in six serials. The vertical restoring force has susceptible to the variation forces for the individual disc springs because the disc spring units are combined in the six serials. The The purpose of this paper is to present two kinds of proposal to improve the quality control of our isolation system and the prediction accuracy of seismic response. The first is to create the the optimal combination method for the disc spring units using the meta-heuristic algorithm to minimize the variation of vertical vertical restoring force. The proposed optimal method was verified through the result of static loading tests using the 72 disc springs which have the half dimensions to full scale. The second is to create a newly analytical model for the friction force caused by polymeric materials. The proposed analytical model was verified by comparing the loading test results. Moreover, the seismic isolation performances were clarified by the seismic response analysis that consider the vertical restoring force of the disc spring units which were combined using the optimal method and the friction force of sliding elements which were modeled by the proposed friction model. This analytical result revealed that our isolation system can reduce the seismic response not only for the high frequency components but also the low frequency ones.
The seismic isolation system consisting of laminated rubber bearings is applied to development of the Sodium-cooled Fast Reactor (SFR) in Japan. While rubber bearings as horizontal isolation system have been expected to be ensured seismic safety margin of components installed in reactor building against horizontal seismic load, vertical isolation systems have been also studied in order to tolerate to the seismic load which has been increased steadily. In this paper, the three dimensional seismic isolation system by combining coned disc springs with rubber bearings is proposed as a concept which consists of isolation devices with abundant track record. Analytical study for this system results that the rocking motion can be suppressed by itself without any suppression system and that the mitigation of vertical response can be enough for buckling design of the reactor vessel simultaneously. In particular, it is important that the vertical natural frequency of system is within the range of 3Hz to 5Hz. Besides, layout, size and stacks of coned discs in the unit of system are studied in order to obtain suitable for specification to SFR buildings.
With no apparent showstopper in sight, the adoption of ArF immersion technology into device mass production is not a matter of 'if' but a matter of 'when'. As the technology matures at an unprecedented speed, many of initial technical difficulties have been cleared away and the use of a protective layer known as top coat, initially regarded as a must, now becomes optional, for example. Our focus of interest has also sifted to more practical and production related issues such as defect reducing and performance enhancement. Two major types of immersion specific defects, bubbles and a large number of microbridges, were observed and reported elsewhere. The bubble defects seem to decrease by improvement of exposure tool. But the other type defect -probably from residual water spots -is still a problem. 1,2 We suspect that the acid leaching from resist film causes microbridges. When small water spots were remained on resist surface after exposure, acid catalyst in resist film is leaching into the water spots even though at room temperature. After water from the spot is dried up, acid molecules are condensed at resist film surface. As a result, in the bulk of resist film, acid depletion region is generated underneath the water spot. Acid catalyzed deprotection reaction is not completed at this acid shortage region later in the PEB process resulting in microbridge type defect formation. Similar mechanism was suggested by Kanna et al, they suggested the water evaporation on PEB plate. 3 This hypothesis led us to focus on reducing acid leaching to decrease residual water spot-related defect. This paper reports our leaching measurement results and low leaching photoresist materials satisfying the current leaching requirements outlined by tool makers without topcoat layer. On the other hand, Nakano et al reported that the higher receding contact angle reduced defectivity. 4 The higher receding contact angle is also a key item to increase scan speed. 5 The effort to increase the receding contact angle become very important issue for not only defectivity but also scanner throughput. Some of our experimental results along this line of study are also included in the report. The last topic covered is LWR (Line Width Roughness) as an essential leverage for performance improvement, especially for the smaller CD that immersion lithography is aiming to define. Our recent effort to find effect and working concept to reduce LWR with low leaching materials is also described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.