Abstract
The latest optical resolution enhancement being applied to integrated circuit (IC) microlithography is based on an idea conceived of over 125 years ago and applied to microscopy ever since [1 ]. Though the technical possibilities of immersion lithography had been considered for several decades, commercial application had not been pursued until very recently, as the incremental extension of optical microlithography appeared to be coming to an end. In the search for a high refractive index fluid compatible with the tools and materials used in IC processing, water has surfaced as the enabling media for this “new” technology [2-4]. The optical properties of water are such that its index increases significantly in the wavelengths region below 250nm. At 193nm, the excitation wavelength of the argon-fluoride (ArF) excimer laser, the refractive index of water is 1.437 while absorption remains low at 0.05 cm-1 [5,6]. The limits of resolution for current generation 193nm lithography were recently considered to occur with the 65 nm IC device generation. Alternative wavelengths in the vacuum ultraviolet (at 157nm from a fluorine excimer laser) or in the extreme ultraviolet (EUV at 13.5nm) were to take over as the semiconductor industry approached these limits. The problem associated with these next generation wavelength technologies is timing, as a host of material and source issues remain as technical challenges requiring solution. Alternatively, by replacing the air space in the image plane of a lithographic imaging lens with water, resolution at 193nm can be enhanced by the increase in refractive power, or 44%. This results in the extension of current optical lithography to sub-45nm device generations.
© 2004 Optical Society of America
PDF ArticleMore Like This
Bruce W. Smith
SWB1 Frontiers in Optics (FiO) 2008
Nigel R Farrar and Tony Yen
PThC3 Photonic Applications Systems Technologies Conference (CLEO:A&T) 2004
Koichi Matsumoto and Takashi Mori
LWA.1 International Optical Design Conference (IODC) 1998