Mueller matrix ellipsometric detection of profile asymmetry in nanoimprinted grating structures

• Published in: Journal of applied physics 2014-11, Vol.116 (19)
• Main Authors: Chen, Xiuguo, Zhang, Chuanwei, Liu, Shiyuan, Jiang, Hao, Ma, Zhichao, Xu, Zhimou
• Format: Article
• Language: English
• Subjects: Applied physics; ASYMMETRY; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPARATIVE EVALUATIONS; DEPOLARIZATION; DETECTION; DIFFRACTION; ELLIPSOMETRY; GRATINGS; Gratings (spectra); MONITORING; NANOSCIENCE AND NANOTECHNOLOGY; Nanotechnology; POTENTIALS; Reciprocity; Reciprocity theorem; SCANNING ELECTRON MICROSCOPY; SENSITIVITY; SYMMETRY
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4902154

Mueller matrix ellipsometry (MME) is applied to detect foot-like asymmetry encountered in nanoimprint lithography (NIL) processes. We present both theoretical and experimental results which show that MME has good sensitivity to both the magnitude and direction of asymmetric profiles. The physics behind the use of MME for asymmetry detection is the breaking of electromagnetic reciprocity theorem for the zeroth-order diffraction of asymmetric gratings. We demonstrate that accurate characterization of asymmetric nanoimprinted gratings can be achieved by performing MME measurements in a conical mounting with the plane of incidence parallel to grating lines and meanwhile incorporating depolarization effects into the optical model. The comparison of MME-extracted asymmetric profile with the measurement by cross-sectional scanning electron microscopy also reveals the strong potential of this technique for in-line monitoring NIL processes, where symmetric structures are desired.