Validation And Application Of A Mask Model For Inverse Lithography - Art. No. 69251j

As photomask critical dimensions shrink significantly below the exposure wavelength and the angle of off-axis illumination increases, the use of Kirchhoff thin mask approximation cannot capture diffraction and polarization effects that occur at a topographical mask surface. Such approximation errors result in inaccurate models that lead to poor prediction for image simulation, which can waste time and money during lithographic process development cycle. The real effects of a thick mask can be simulated using finite difference time domain (FDTD) electromagnetic (EM) field calculations, or be better approximated with less error using such techniques such as boundary layer or various Fourier transformation techniques.