Hk. Oh et al., MULTIPLE THIN-FILM INTERFERENCE EFFECT ON 0.25-MU-M LINE-WIDTH VARIATION IN OPTICAL LITHOGRAPHY, Journal of the Korean Physical Society, 30, 1997, pp. 273-278
The line width variations with illumination type and with sublayer are
studied for deep UV light source and developed 0.25 mu m isolated lin
e pattern. The line width variation is the result of the reflectivity
variation caused by multiple thin film interference effect. Off-axis i
llumination makes larger variation due to the larger reflectance and w
orse aerial image at best focus. The line width varies a lot with the
total reflectance and depends on the optical properties and the thickn
esses of sublayers. Antireflection coating should be used in order to
control the line width variation. The desired variation of less than 0
.05 mu m can be obtained with 0.19 mu m thick ARC whose refractive ind
ex is 1.663+0.2i.