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5 April 2012 Investigation of E-beam patterned nanostructures using Mueller Matrix based Scatterometry
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Scatterometry is one of the most useful metrology methods for the characterization and control of critical dimensions (CD) and the detailed topography of periodic structures in microelectronics fabrication processes. Spectroscopic Ellipsometry (SE) and Normal Incidence Reflectometry (NI) based Scatterometry are the most widely used methodologies for metrology of these structures. Evolution of better optical hardware and faster computing capabilities led to the development of Mueller Matrix (MM) based Scatterometry (MMS). In this paper we present the first study of dimensional metrology using full Mueller Matrix (16 element) Scatterometry in the wavelength range of 245nm- 1000nm. Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light through a sample. MM is a 4x4 transformation matrix (16 elements) describing the change in the intensities of incident polarized light expressed by means of a Stokes Vector. The symmetry properties associated with MM provide an excellent means of measuring and understanding the topography of the periodic nanostructures. Topography here refers to uniformity of the periodic structure. The advantage of MMS over traditional SE Scatterometry is the ability of MMS to measure samples that have anisotropic optical properties and depolarize light. The present study focuses on understanding the precision and accuracy of Mueller based Scatterometry with respect to other methodologies by a systematic approach. Several laterally complex nanoscale structures with dimensions in the order of nanometers were designed and fabricated using a state of the art E-beam pattering tool (VISTEC [R] 300). Later, Spectroscopic Mueller matrix (all 16 elements) and SE data were collected in planar diffraction mode for the samples using J.A. Woollam RC2 [TM] Spectroscopic Ellipsometer. NanoDiffract [TM] (Scatterometry software provided by Nanometrics Inc.) was used to model the nanostructures to precisely calculate the critical dimensions. Complementary techniques like SEM were used to compare the results obtained from Scatterometry. Finally, Mueller and SE based Scatterometry techniques were compared commenting on reliability of MM based Scatterometry.
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Gangadhara Raja Muthinti, Brennan Peterson, and Alain C. Diebold "Investigation of E-beam patterned nanostructures using Mueller Matrix based Scatterometry", Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83240O (5 April 2012);

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