Anisotropy Effects In Real-Time Optical Diagnostics Of Epitaxial Growth And Associated Metrology Instrumentation

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Title: Anisotropy Effects In Real-Time Optical Diagnostics Of Epitaxial Growth And Associated Metrology Instrumentation
Author: Asar, Muharrem
Advisors: David Aspnes, Committee Chair
Abstract: As new applications in metrology force the evolution of accuracies from the 1-2% range characteristic of rotating-polarizer and rotating-analyzer ellipsometers to 0.1-0.2%, ellipsometric technology is rapidly moving to rotating-compensator designs. In addition, new classes of artifacts become relevant. This work is a thorough investigation of various effects related to optically anisotropic components and samples, including the monoplate compensator, the effect of axial misalignments on the accuracy of ellipsometric measurements, and the effect of sample anisotropy on ellipsometric data obtained during real-time measurements of epitaxial growth. Advances include generalization of the Jones-matrix formulism to 3 dimensions to describe axially misaligned components, an improvement of the widely used formulation of Yeh that eliminates singularities in the calculation of transmittance and reflectance properties of anisotropic materials, and a Taylor-series approach to calculate the effect of thin anisotropic surface layers on complex reflectances thereby avoiding the need to diagonalize matrices. I provide the first analysis of the monoplate compensator, a next-generation device for broadband spectroscopic ellipsometry, showing that the even Fourier coefficients in the transmitted intensity in instruments using this device provide information about the sample and odd coefficients about system alignment, with the even coefficients affected only to second order in misalignment parameters. Alignment procedures are developed, and misalignments that create other types of artifacts in the determination of surface anisotropies in rotating-sample OMCVD reactors that are analyzed and discussed. In general, the work provides new insight into the treatment of the properties of optically anisotropic materials in both data analysis and metrology instrumentation, and allows for increased accuracy in the analysis of ellipsometric data.
Date: 2005-04-18
Degree: PhD
Discipline: Physics

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