The stable performance of the line-narrowed krypton fluoride excimer laser for production steppers, the KLES-G6, in real stepper mode operation is presented. Wavelength stability of <+1-0.1 pm and pulse-to-pulse energy stability of < 2% ( c ) have been achieved in the real stepper mode operation. In addition the durability test has been made at 6 W (10 mJ, 600 Hz) in 1 sec. ON -1 sec. OFF (50%) burst mode and in cw mode. The central wavelength stability <+/-0.2 pm including the drift at the head of burst, spectral bandwidth < 1.5 pm, and pulse-topulse energy stability < 2.5 % ( a ) over 1.6 x109 shots have been achieved. The KLES-G6 is going to help the excimer laser stepper to be employed in the real commercial production successfully.

A narrow band KrF excimer laser system for lithography has been developed. Its durability has been proved up to 2 billion shots that correspond to one year operation in mass production line. The system has kept the average power of 6W with the power stability within +-3? and the spectral line-width 1.2 pm (FWHM) with the wavelength stability within +-0.2 pm. The integration of the spectrum has indicated that 95? of the spectral energy lay inside 4.6 pm band during 2 billion shots. L INTRODUCTIONThe optical micro-process technology for 0.3 micron or less is already established experimentally both by i-line phase shift method and narrow band KrF excimer laser method in several laboratories. Recently several laser manufacturers have developed 4W output narroç band KrF excimer laser devices for practical lithography 1)2) They are operated in the sample production process of ULSI ICs. The next target of excimer laser lithography is the improvement of productivity for the mass production process. The most important technology for it is relating to the excimer laser device itself. Therefore, the advent of the laser with high stability, reliability and low running cost is expected seriously.We compared the several narrowing methods in the previous jtper presented at last Optical/Laser Microlithography Symposium °.In this paper we shall introduce the KLES-G6 narrow band KrF excimer laser system for the mass production process. We have proved its durability up to 2 billion shots which correspond to one year operation in the mass production line. 532 / SPIE Vol. 1674 Optical/Laser Microlithography V (1992) 0-81 94-0829-8/92/$4.OO Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx L SYSTEM DESCRIPTION 2.1 SYSTEM The appearance of the KLES-G6 Is shown In Figure 1. The footprint is minimized to save the area in super clean factories. The operating conditions, maintenance status and interlock informations can be monitored by a remote control paddle (hanged on the front panel).The schematic block diagram of the laser is shown in Figure 2. This laser is specialized for a microlithography application. It employs an advanced spectrum control system with a precise wavelength monitor and a power stabilization system with a precise pulse energy monitor. The power and spectrum are stabilized by the feed-back system. The initial laser setting and the gas supplement are managed by the main control unit. The laser operation parameters, maintenance status and interlock informations are communicated between stepper and main control unit. The status of laser can be checked both by the remote control paddle and by an external personal computer. Figure 1 Appearance of the KLES-G6. SPIE Vol. 1674 Optical/Laser Microlithography V (1992) / 533 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspxFigure 2 Schematic block diagram of KLES-G6._i SPECTRAL MONITOR As w fully described t...

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The conventional line-narrowing methods employed by narrow band KrF excimer lasers are intra-cavity etalons method and a Littrow grating with beam expansion method. They have the following problems in high average power operation; a)short lifetime of the etalons and large wavelength drift and large line-width change(the etalons method) or b)low output power and short lifetime of electrodes(the grating method).To solve the above problems, we propose a hybrid method consisting of two prism beam expanders, an etalon and a Littrow grating. These prism beam expanders decrease the light intensity on the etalon, so that the lifetime of the etalon is increased drastically, the passive wavelength drift is minimized, and the wavelength is adjusted quickly. By employing this system, we got average power of more than 8 W, line-width of less than 2.5 pm(FWHM) and long term wavelength stability of less than pm.