M. Erdelyi et al., GENERATION OF DIFFRACTION-FREE BEAMS FOR APPLICATIONS IN OPTICAL MICROLITHOGRAPHY, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 15(2), 1997, pp. 287-292
A new concept based on a Fabry-Perot interferometer for the generation
of nondiffracting Bessel beams is described and proposed for potentia
l applications in microlithography such as the fabrication of small is
olated patterns. It was experimentally demonstrated that the depth of
focus can be increased by a factor of about 2, and simultaneously the
transverse resolution improved by a factor of 1.6, when using this tec
hnique to image contact holes. The properties of simultaneous imaging
of two contact holes were also investigated. It was shown experimental
ly that, even in the most critical case (when the first diffraction ri
ngs overlap), undesirable interference effects between the adjacent co
ntact holes can be eliminated by means of a phase shifting technique.
(C) 1997 American Vacuum Society.