Haghtalab Mohammad, Faraji-Dana Reza
Center of Excellence on Applied Electromagnetics Systems, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran, Iran.
J Opt Soc Am A Opt Image Sci Vis. 2012 May 1;29(5):748-56. doi: 10.1364/JOSAA.29.000748.
Analysis and optimization of diffraction effects in nanolithography through multilayered media with a fast and accurate field-theoretical approach is presented. The scattered field through an arbitrary two-dimensional (2D) mask pattern in multilayered media illuminated by a TM-polarized incident wave is determined by using an electric field integral equation formulation. In this formulation the electric field is represented in terms of complex images Green's functions. The method of moments is then employed to solve the resulting integral equation. In this way an accurate and computationally efficient approximate method is achieved. The accuracy of the proposed method is vindicated through comparison with direct numerical integration results. Moreover, the comparison is made between the results obtained by the proposed method and those obtained by the full-wave finite-element method. The ray tracing method is combined with the proposed method to describe the imaging process in the lithography. The simulated annealing algorithm is then employed to solve the inverse problem, i.e., to design an optimized mask pattern to improve the resolution. Two binary mask patterns under normal incident coherent illumination are designed by this method, where it is shown that the subresolution features improve the critical dimension significantly.
本文提出了一种通过快速准确的场论方法对多层介质纳米光刻中的衍射效应进行分析和优化的方法。通过使用电场积分方程公式，确定了由TM偏振入射波照射的多层介质中任意二维（2D）掩模图案产生的散射场。在该公式中，电场由复镜像格林函数表示。然后采用矩量法求解所得的积分方程。通过这种方式，实现了一种准确且计算效率高的近似方法。通过与直接数值积分结果进行比较，验证了所提方法的准确性。此外，还对所提方法得到的结果与全波有限元方法得到的结果进行了比较。将光线追踪方法与所提方法相结合，以描述光刻中的成像过程。然后采用模拟退火算法来解决逆问题，即设计优化的掩模图案以提高分辨率。通过该方法设计了两种在正常入射相干照明下的二元掩模图案，结果表明亚分辨率特征显著提高了临界尺寸。
