Contrast in the evanescent near field of lambda/20 period gratings for photolithography.
Light propagation through gratings with periods as small as lambda/20 is investigated computationally by use of the multiple multipole method in two dimensions. High image contrast is evident close to the grating. Strong evanescent decay of the high spatial frequency components is observed with the region of high contrast shrinking linearly as the period of the grating is decreased. Simulations were performed for TE and TM polarizations with the TM polarization providing the dominant contrast compared with TE, which is strongly attenuated owing to the polarizing effect of the gratings. These results show good promise for optical contact lithography in the evanescent near field of a shadow mask to attain feature sizes smaller than lambda/20.
McNab
S J
SJ
Department of Electrical and Electronic Engineering, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. s.mcnab@elec.canterbury.ac.nz
Blaikie
R J
RJ