• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.1-8
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• 1994

A five mirror system with a reduction magnification(M=+1/5) is designed for DUV optical lithography. First, for spherical mirror systems, the numerical solutions of all zero 3rd order aberrations are derived and the 3-dimensional shape of the solution-domain is obtained. In these solutions, we select solutions which have as less residual aberrations and smaller central obscurration as possible and the aspherization is carried out to the last two spherical mirrors to obtain a system that has as higher NA as possible. Finally we obtain the system of which NA is 0.45, the central obscuration is about 25% and the resolution is about 650 cycles/mm at the 50% MTF value criterion and the depth of focus of 0.8${\mu}m$ for the nearly incoherent illumination (${\sigma}$=1.0) and the wavelength of 0.193${\mu}m$ (ArF excimer laser line).

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.188-200
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• 1995

A design of unit magnification 2-mirror system with high resolution is presented. It is for soft X-ray(wavelength of 13 nm) projection imaging and suitable for preparation of high density semiconductor chip. In general, a holosymmetric system with unit magnification has the advantage that both coma and distortion are completely eliminated. In our holosymmetric 2-mirror system, spherical aberration is addtionally removed by using two identical paraboloidal mirror surfaces and field curvature aberration is also corrected by balancing Petzval sum and astigmatism which depends on the distance between two mirrors, so that the system is a aplanatic flat-field paraboloidal 2-mirror holosymmetric system. This 2-mirror system is small in size, and has a simple configuration with rotational symmetry about optical axis, and has also small central obscuration. Residual finite aberrations, spot diagrams, and diffraction-based MTF's are analyzed for the check of performances as soft X-ray lithography projection system. As a result, the image sizes for the resolutions of$0.25\mum$and $0.18\mum$are 4.0 mm, 2.5 mm respectively, and depths of focus for those are $2.5\mum$, $2.4\mum$respectively. This system should be useful in the fabrication of 256 Mega DRAM or 1 Giga DRAM. DRAM.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.143-149
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• 2005

KASI (Korea Astronomy and Space Science Institute) is developing the near-infrared camera system named KASINICS (KASI Near-Infrared Camera System) which will be installed at the 60cm f/13.5 Ritchey-Chretien telescope of the Sobaeksan Optical Astronomy Observatory (SOAO). The camera system is optimized for JHKL bands and has a 6 arcmin FOV. The optical system consists of two spherical mirrors and a 8-position filter wheel. With the exception for the dewar window, all optical elements are cooled inside cryogenic dewar. Since the Offner system is adopted to prevent thermal noises from outside of the telescope primary mirror, the secondary mirror of the Offner system acts as a cold Lyot stop. The optical performance does not change by temperature variations because the Aluminum mirrors contract and expand homogeneously with its mount. We finished the design and fabrication of the optical parts and are now aligning the optical system. We plan to have a test observation on 2006 January.