The DUV-VUV laser microlithography technology is main player from 250 nm to 70 nm node LSI patterningprocess. Trend of DUV light source device for micro-lithography is described. Also this paper reports thetechnical issues of VUV laser microlithography and F₂ laser light source, and introduces the technical approachand some latest results of the F₂ lithography technology development project in ASET.

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EUV (Extreme Ultra-Violet) lithography is most promising technology after 50 nm technology node fromaround 2007. There are many problems in order to realize EUV lithography and the most serious problem is todevelop the EUV source. A debris free EUV source with a collectable radiation power of 50 W to 150 W atover 5 kHz in the spectral range of 13-14 nm will be required to achieve a 300 mm wafer throughput of up to 80 wafer/hour. Several types of laser produced plasmas (LPP 's) and gas discharge based plasmas (EUV lamps) are under investigation as EUV sources. However, there are big differences between the status quo and therequired specification. In this review, the status of EUV source candidates is introduced and future direction ofdevelopment will be briefly commented.

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This paper describes several kinds of electron beam sources and their gun structures for a semiconductorlithography system. In general, high brightness LaB₆ thermal-emission type is very common due to the lowworkfunction advantage. However, for an electron-beam projection lithography system (EPL), the high emittance (low brightness) gun should be required in order to achieve excellent illumination uniformity even in theone large exposure field. Furthermore, the direct-bombardment Ta cathode and a unique illumination opticsare needed. They result in excellent pattern line-width fidelity. For the future node devices, a mask-less lithographysystem is also expected. For this purpose, various kinds of multiple beam sources are described. Insummary, optimized electron sources and gun structures should be required along with the suitable electronbeam lithography for every node device.

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Synchrotron-based proximity x-ray lithography (PXL) has been developed for more than 20 years. The lightsource for high-throughput PXL manufacturing is a synchrotron radiation (SR) ring with multiple x-ray steppers. From the late 1980 's to early 1990 's, many compact SR rings for PXL adopted superconducting magnetsfor achieving their compactness were built in the USA and Japan. The Association of Super-Advanced Electronics Technologies (ASET) was established in Japan in 1996 and ASET had several programs to promote PXL in NTT at Atsugi-shi. An e-beam X-ray mask writer “EB-X3” was developed by NTT and ASET fabricated PXL masks for 4Gbit DRAMs by the writer with 100nm design rules. Sumitomo Heavy Industries (SHI) has developed a new normal-conducting compact SR ring “AURORA-2S” with a beam current 500mA usinga novel idea to increase the field strength of normal-conducting magnets to 2.7 Tesla. In this paper, SR rings for PXL are introduced.

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Laser-produced plasma EUV source for EUV lithography has been developed. Intensity of 13.5 nm EUV andamount of debris from irradiated various targets with pulsed YAG laser (1J, 7ns) were estimated. 0.02-0.2μJ/cm²/pulse of 13.5 nm EUV at x-ray CCD-camera equipped with the spectrometer for Cu-tape target. Si₃N₄filter had kept more than 60% transmission for EUV within 100, 000 laser shots. 2 hour exposureof 13.5nm EUV on EUVL resist (SAL601) were demonstrated.

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A simple model for calculating the photoionization rate in AVLIS system is proposed. It was found that, forthe different incident laser conditions, the dependence of photoionization rate of target atom on the propagation distance estimated by the model represents well the simulation result. It has been confirmed that thismodel is useful for analyzing the performances of AVLIS plant without simulation.

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In AVLIS system, the laser pulses propagate through an atomic vapor for a long distance. It has been shown bycomputer simulation that the laser interactions with target and non-target atoms modify the laser pulse shapeand propagation velocity, resulting in the degradation of photoionization rate of target atom. In the previouspaper, a simple model was proposed for calculating photoionization rate without computer simulation in theresonant media. In order to apply this method to the mixture of resonant and near-resonant atoms, the modelwas modified by introducing the decrease of laser propagation velocity by a near-resonant interaction. Basedon this model, a simple formula was derived to connect the effective propagation distances in the resonantmcdia and the mixturc. It was found that, for the different incident laser conditions, the dependence of photoionizationrate calculated by using the simple formula represent well the simulation results.

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This paper describes the experimental and computational results of an increase of the linear-zone in a beamobscuration focusing sensor. Using the sectorially obscured returning beam the linear-zone was increasedcompared to that of the half obscured beam method. The calculated values of the focus sensing characteristicsclosely agree with the experimentally measured values. When the central angle of a sectorial beam wasreduced to 25 degrees from 90 degrees, the linear-zone increased to 15.7μm from 2.2μm. However, when thecentral angle of a sectorial beam was reduced to 90 degrees from 180 degrees, the linear-zone was not changed.

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Image relaying in a high-average-power slab laser system, especially one with thermal lenses, was studied.Ray-trace analysis using an ABCD matrix was conducted for a multi-cascade relaying system. The analysisclarified quantitatively the beam expansion, the focal shift and the power loss by thermal lenses that should betaken into account in the system design. An Nd: YAG slab laser system was developed, and its beam wasrelayed successfully by careful design, taking the above considerations into account. The laser system demonstratedan average power of 235 W with a high beam quality.

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