Several approaches to printing 50/50 nm nested contact holes are described and compared using lithographic simulations (ProlithTM 7.1). The approaches used include: off-axis quadrupole illumination and attenuating phase-shift mask with optimized polarization of the illumination; chromeless alternating phase shift-masks (CAPSM) in conjunction with special polarization schemes; immersion lithography with extremely high numerical aperture (NA) at 157 nm wavelengths; and EUV lithography. We show how the limits of the off-axis illumination technique can be pushed with the use of radial polarization and how the mask bias (or background transmission) can be used to optimize the image. Resolution limits are further pushed with 2D chromeless alternating PSM combined with the radial polarization. We show that with radial polarization, high-contrast images can be obtained and high-quality contact holes at 100 nm pitch can be printed using negative photo-resist. It is shown that, with immersion in a liquid of refractive index equal to 1.5, standard attenuating PSM with quadrupole or quasar illumination with unpolarized light and positive photo-resist will allow the printing of 100-nm-pitch contact holes. We compare these findings with results obtained at an EUV wavelength to confirm that imaging at an EUV wavelength and low NA can also provide excellent conditions to print 100-nm-pitch contact holes.
Daniel Cote, David Ahouse, Daniel Galburt, Hilary Harrold, Justin Kreuzer, Mike Nelson, Mark Oskotsky, Geoffrey O'Connor, Harry Sewell, David Williamson, John Zimmerman, Richard Zimmerman
The never ending drive for faster and denser ICS has reached a staggering pace is attributable to the economics of the semiconductor industry and competition among chip manufacturers. This quest may be approached in different ways. A common approach is to continue to push the 248nm wavelength lithographic tools. This paper reviews the status of 193nm lithography with respect to its production worthiness, capability and extendibility when compared to 248nm systems. Key issues such as cost of ownership and process maturity are discussed. Analytical results, system analyses and recent lithographic results are presented. Conclusions are offered with respect to the logical timing of the insertion of 193nm lithography tools into semiconductor manufacturing.
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