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`EXHIBIT
`DSS-2006
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`DSS—2 006
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`EXHIBIT
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`3/3/2015
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`Willson Research Group Research Immersion
`
`Willson Research Group
`The University of Texas at Austin
`
`Immersion
`Lithography
`Theory
`Resist Extraction
`Measurements
`2nd Gen Immersion
`Fluid
`Anomalous Dispersion
`Modelling
`Publication
`Research Team
`Links
`
`Library
`
`Willson
`
`Teaching
`
`Research
`People
`Links
`Immersion Lithography
`
`Introduction
`
`Semiconductor microlithography is the primary process for printing circuit patterns
`for microelectronic devices. In this process a substrate such as a silicon wafer is
`coated with a polymer film known as a photoresist. Portions of the film are then
`exposed to narrow band width UV radiation that is passed through a partially
`chromeplated quartz mask and focused with a lens system. This exposure
`generates a solubilityswitching reaction in the photoresist, rendering a portion of
`the film soluble in an aqueous base developer. When the exposed regions of the
`film are rendered soluble, the resulting relief is called a positive tone image. When
`the exposed regions become insoluble, the process is referred to as negative
`tone. The remaining resist acts as an etch mask while the pattern is transferred
`into the underlying substrate before being stripped.[1]
`
`Background
`
`Figure 1
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`The resolution (R) of the lithographic process is defined by the Rayleigh Equation,
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`where k1 is known as the Rayleigh coefficient, is the vacuum wavelength of the
`exposing radiation, n is the index of refraction of the ambient medium through
`which the exposing radiation is focused, is the angular half aperture of the lens
`and NA stands for the numerical aperture of the lens. [2]
`
`Improvements in lithographic patterning have led to the continual shrinking of
`device feature sizes and the resulting performance improvements and cost
`reductions seen in today’s electronic devices. These improvements have
`historically been achieved through the development of new exposure sources with
`lower wavelengths. Accompanying incremental improvements in the lens system
`by the reduction of k1 and the increase of NA through larger q’s have also
`contributed.
`
`Early exposure tools used 436 nm light from the gline emission of a mercury arc
`lamp, followed by 365 nm light from its iline emission. Kryptonfluorine (KrF)
`excimer lasers then replaced mercury arc lamps for leading edge lithography with
`248 nm light, and the state of the art is now argonfluorine (ArF) lasers producing
`light at 193 nm.
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`Illustration of exposure through mask and focusing by lens.
`
`With each step down in wavelength, optical systems had to be redesigned and
`new materials have had to be developed.[3] To move below 193 nm, the
`development is complicated by the need for completely new materials for the lens
`systems as well as the photoresist platforms and the necessity for exposure to
`take place in vacuum. The rising costs of such development has led to the
`resurrection of a novel lithographic process first proposed in the 1980s called
`immersion lithography.[4][5][6][7] Immersion lithography with the 193 nm
`exposure wavelength is now considered the most likely candidate for printing
`features at 45nm and below.[8]
`
`Continue to Immersion Lithography Theory
`
`References
`
`1. Thompson, L.F.; Willson, C.G.; Bowden, M.J. Introduction to Microlithography.
`American Chemical Society, Washington, DC. 1989.
`
`2. M. Switkes, M. Rothschild, R. R. Kunz, SY. Baek, D. Cole, M. Yeung,
`Microlithography World 12(2), 4, 2003.
`
`3. Stewart, M.D.; Patterson, K.; Somervell, M.H.; Willson, C.G. J. Phys. Org.
`Chem. 2000; 13: 767774.
`
`4. A. Takanashi et al., US Patent No. 4480910, 6 Nov. 1984
`
`5. Lin, B. J. Microelectron. Eng.1987, 6, 31.
`
`6. Kawata, J.; Carter, J. M.; Yen, A.; Smith, H. I. Microelectron. Eng. 1989, 9, 31.
`
`7. H. Kawata, I. Matsumura, H. Yoshida, K. Murata, Jpn. J. Appl. Phys. 31, 4174,
`1992.
`
`8. International Technology Roadmap for Semiconductors: http://public.itrs.net/
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`Version History
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`http://willson.cm.utexas.edu/Research/Sub_Files/Immersion/index.php
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`Willson Research Group Research Immersion
`Original page created 02/23/06
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`© 2015 Willson Research Group, The University of Texas at Austin
`
`Last updated Friday, August 3, 2012. Site best viewed in Firefox
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