The semiconductor industry is continually challenged to maintain the trend
identified in 1965 by Gordon Moore of increasing the density of transistors on an
integrated circuit. These advances have been achieved by increasing the resolution that
can be printed with photolithography, traditionally by decreasing the exposure
wavelength. Decreasing the exposure wavelength from 193 nm, the current state of the
art, presents significant technical challenges. To circumvent these challenges, resolution
can be increased by enabling increases in numerical aperture (without changing the
exposure wavelength), using immersion lithography. In immersion lithography, the air
gap between the photoresist-coated wafer and lens is replaced with a high refractive
index fluid. Immersion lithography has been demonstrated with water as the immersion
fluid. With water immersion lithography at 193 nm, the maximum resolution that can be
printed can be decreased from 65 nm to 45 nm. To enable further resolution increases,
immersion fluids with a higher index than water are needed. The requirements for next generation high index fluids are: an index of refraction higher than water, high
transparency, and physical properties similar to water.
A variety of methods to identify a high index fluid were completed. First, the
optical properties of aqueous solutions of metal cations with varying anions were tested.
A series of linear, cyclic, and polycyclic alkanes were also studied, since saturated
systems have electronic transitions at wavelengths less than 200 nm, to provide the
necessary transparency at 193 nm. Large alkane groups were also incorporated into
either the cation or anion of a salt to develop an aqueous solution with the optical
properties of a saturated hydrocarbon. In addition to these empirical surveys, a modeling
approach was used to develop “designer” absorbance spectra that would correspond to
fluids with a high index and low absorbance at 193 nm.
Additionally, in Appendix D, the results of an electrochemical study of the
diffusion coefficient of ferrocene methanol in poly(ethylene glycol) diacrylate hydrogels
of varying molecular weight and water content will be presented. The results of these
mass transport studies can be used to qualitatively understand the mass transport
characteristics of additional species in the hydrogel. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/7578 |
| Date | 02 June 2010 |
| Creators | Costner, Elizabeth A. |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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