Schematic layout of the experimental IIL tool with 244-nm laser source, 0.9 NA Cheetah objective lens and real-time focusing system.
Schematic layout of the reduction telecentric imaging geometry showing imaging and illumination rays and relative positions of lenses and relayed planes.
PROLITH™ simulations of IIL were used prior to the experiment to provide insight into resolution and exposure strategies. (a) 3-exposure IIL for a CD of , ends of the lines are well defined, isolated lines are cleared; and (b) the pupil plane filter used in the off-axis exposures (left and right filters) and low-frequency exposure (center filter).
SEM of PR lines with a CD of , demonstrating that the optical system has the expected spatial frequency bandwidth. Those lines were exposed using a mask and a single off-axis exposure without any pupil plane filter.
(a) SEM of developed PR for 3-exposure IIL for a CD of at a 244-nm wavelength and 0.9 NA. Isolated lines and the square edge of the box are well defined, dense lines are cleared; (b) modeling of 3-exposure IIL for a CD of for an overexposed condition; shows the same hole in the middle of the square implying that this feature on the pattern is due to exposure issues not to the imaging.
Specifications for the 0.9 NA TROPEL Cheetah lens.
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