Mueller based scatterometry and optical characterization of semiconductor materials

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 found in microelectronics fabrication processes. Spectroscopic ellipsometry (SE) and normal incidence reflectometry (NI) based scatterometry are the most widely used optical 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). Dimensional metrology using full Mueller Matrix (16 element) scatterometry in the wavelength range of 245nm-1000nm was discussed in this work. Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light reflected from 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 order of arrayed 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 work focuses on understanding the Mueller based Scatterometry with respect to other methodologies by a systematic approach. Several laterally complex nano-scale structures with dimensions in the order of nanometers were designed and fabricated using e-beam lithography. Also Mueller based analysis was used to extract profile information and anisotropy coefficients of complex 3D FinFET, SOI fin grating structures. Later, Spectroscopic Mueller matrix (all 16 elements) and SE data were collected in planar diffraction mode for the samples using a J.A. Woollam RC2™ Spectroscopic Ellipsometer. NanoDiffract™ (Scatterometry software provided by Nanometrics Inc.) was used to model the nanostructures to precisely calculate the critical dimensions. Complementary techniques like SEM were compared with the results obtained from scatterometry. Mueller and SE based scatterometry techniques were compared commenting on reliability of MM based scatterometry.