Resolution enhancement by aerial image approximation with 2D-TCC
Kenji Yamazoe, Yoshiyuki Sekine, Miyoko Kawashima, Manabu Hakko, Tomomi Ono, Tokuyuki Honda · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
A newly developed sub-resolution assist feature (SRAF) placement technique with two-dimensional transmission cross coefficient (2D-TCC) is described in this paper. In SRAF placement with 2D-TCC, Hopkins' aerial image equation with four-dimensional TCC is decomposed into the sum of Fourier transforms of diffracted light weighted by 2D-TCC, introducing an approximated aerial image so as to place SRAFs into a given reticle layout. SRAFs are placed at peak positions of the approximated aerial image for enhanced resolution. Since the approximated aerial image can handle the full optical model, SRAFs can be automatically optimized to the given optical condition to generate the optimized reticle. The validity of this technique was confirmed by experiment using a Canon FPA6000-ES6a, 248 nm with a numerical aperture (NA) of 0.86. A binary reticle optimized by this technique with mild off-axis illumination was used in the experiment. Both isolated and dense 100 nm contacts (k1 = 0.35) were simultaneously resolved with the aid of this technique.