Quartz inhomogeneity effects in diffraction-limited deep ultraviolet imaging.
In the investigation of the imaging performance of a high-N.A. deep ultraviolet lens for submicrometer lithography, a ghost image was detected that was displaced from the main image. The origin of the ghost was traced to periodic variations in the index of refraction of a fused-silica beam splitter in the optical column. Several different beam splitters exhibited the ghost aberration; each had small but detectable index striations, presumably related to the manufacturing process. The measurement of the diffraction efficiency of the resulting phase grating showed a strong wavelength dependence. The relatively large diffraction efficiency at 248 nm produced secondary ghost images of ~2% relative intensity.
Pfau
A K
AK
Partlo
W N
WN
Hsu
R
R
Oldham
W G
WG