Rigorous FEM simulation of EUV masks: influence of shape and material parameters

Abstract

We present rigorous simulations of EUV masks with technological imperfections like side-wall angles and corner roundings. We perform an optimization of two different geometrical parameters in order to fit the numerical results to results obtained from experimental scatterometry measurements. For the numerical simulations we use an adaptive finite element approach on irregular meshes. 1 This gives us the opportunity to model geometrical structures accurately. Moreover we comment on the use of domain decomposition techniques for EUV mask simulations. 2 Geometric mask parameters have a great influence on the diffraction pattern. We show that using accurate simulation tools it is possible to deduce the relevant geometrical parameters of EUV masks from scatterometry measurements.This work results from a collaboration between AMTC (mask fabrication), Physikalisch-Technische Bundesanstalt (scatterometry) and ZIB/JCMwave (numerical simulation).

Scatterometry sensitivity analysis for conical diffraction versus in-plane diffraction geometry with respect to the side wall angle

“…In recent years we investigated goniometric EUV scatterometry at line-grating test structures with respect to the determination of the line profile parameters like width, height and side wall angle (SWA) . [1][2][3][4] With respect to width and height the attainable uncertainties are well in line with the requirements of the ITRS metrology roadmap. For the SWA, however, the required uncertainty well below 1 • is still challenging for metrology and mask manufacturing.…”

Finite element models of lithographic mask topography

“…Previously, the solver has been used, int. al., in studies and metrological investigations of DUV and EUV masks [7][8][9].…”

Rigorous simulation of 3D masks

“…This can be, e.g., caused by uncertainties in the geometry of the sample. As has been shown in different works 16 the high accuracy and speed of rigorous FEM simulations can be utilized to obtain precise informations about the sample geometry or material parameters by optimizing the deviation from experimentally obtained data.…”