It is of tremendous impact with multilayer defects, which are caused by particles, substrate pits or scratches, in EUV lithography for the high volume manufacturing. Multilayer defects suppress the productivity and utilization rate of the mask blank. In this paper, we did a thorough investigation by conducting imaging simulations on dense and semi-dense patterns including lines and contact holes. The impact of isolated multilayer defects on the imaging of 22nm half-pitch dense line/contact and 33nm half-pitch semi-dense line has been studied, and the CD errors are calculated. The CD error, caused by the planar defect which is smoothed out during the multilayer deposition process, is found to be within ±10% of target values. This CD error can be compensated by adjusting the exposure dose or local pattern size. In contrast, the non-planar defect, which is not being smoothed in the multilayer surfaces, would lead to severe damages to the lithography performance.
With the continuous shrink of feature sizes, the 3D mask effects cannot be ignored in computational lithography. 3D mask effects inducing focus shift and scalar aberration like spherical aberration have been studied very well. To our knowledge, the polarization aberration (PA) including scalar aberration, retardance and diattenuation caused by 3D mask effects have not been paid attention to, which is very significant for computational lithography in advanced node. In this paper, we propose a novel approach to derive the PA induced by 3D mask effects from the diffraction frequency spectrum between the rigorous electromagnetic field model and the Kirchhoff model and express it as Jones matrix pupil. In addition, the physical decomposition of Jones matrix is adopted to obtain five physical properties of polarization aberration induced by 3D mask. Thus, the proposed method can fully, quantitatively, and clearly describe the PA induced by 3D mask.