Optical metrology of thickness and indium composition of epitaxial InxGa1−xAs layers on Si substrates
An optical metrology solution using a Spectroscopic Ellipsometer (SE) tool has been demonstrated to monitor the thickness and indium composition of InxGa1-xAs layers on Si substrates for III-V compound semiconductor channel devices. Fundamentally, the SE tool is based on light interference and phase shift effects corresponding to individual material properties. A wide range of wavelengths (190 ~ 840nm) of the SE spectra is used to collect elliptically polarized light and for dispersion model characterization to float n and k values at each wavelength. The SE data for InxGa1-xAs and indium composition is quantified using TEM (Transmission Electron Microscopy) and RBS (Rutherford Backscattering Spectrometry) showing excellent correlation. In the range of 190nm to 840nm wavelengths SE is able to provide InxGa1-xAs layer thickness through post data processing using InxGa1-xAs/GaAs layer thickness with surface roughness consideration. Reducing the surface roughness is expected to enable more accurate and higher intensity of elliptically polarized light from films so that the best film model can be applied to float n and k values. Indium composition of the InxGa1-xAs layer is quantified by dispersion (n and k) values extracted from a specific wavelength. In this work, the n value of InxGa1-xAs/GaAs film stack at 219nm shows excellent proportional relationship with RBS data on three different indium compositions, while k value at 248nm shows excellent inverse relationship. This is a promising solution to evaluate critical growth parameters such as indium composition and to offer detailed and immediate feedback on the deposition process. This solution can be extended to other compound materials - characterizing thickness and composition by correlating n and k values for each wavelength.
Spectroscopic Ellipsometry: Principles and Applications
Foreword. Preface. Acknowledgments. 1 Introduction to Spectroscopic Ellipsometry. 1.1 Features of Spectroscopic Ellipsometry. 1.2 Applications of Spectroscopic Ellipsometry. 1.3 Data Analysis. 1.4 History of Development. 1.5 Future Prospects. References. 2 Principles of Optics. 2.1 Propagation of Light. 2.2 Dielectrics. 2.3 Reflection and Transmission of Light. 2.4 Optical Interference. References. 3 Polarization of Light. 3.1 Representation of Polarized Light. 3.2 Optical Elements. 3.3 Jones Matrix. 3.4 Stokes Parameters. References. 4 Principles of Spectroscopic Ellipsometry. 4.1 Principles of Ellipsometry Measurement. 4.2 Ellipsometry Measurement. 4.3 Instrumentation for Ellipsometry. 4.4 Precision and Error of Measurement. References. 5 Data Analysis. 5.1 Interpretation of (PSI, DELTA). 5.2 Dielectric Function Models. 5.3 Effective Medium Approximation. 5.4 Optical Models. 5.5 Data Analysis Procedure. References. 6 Ellipsometry of Anisotropic Materials. 6.1 Reflection and Transmission of Light by Anisotropic Materials. 6.2 Fresnel Equations for Anisotropic Materials. 6.3 4x4 Matrix Method. 6.4 Interpretation of (PSI, DELTA) for Anisotropic Materials. 6.5 Measurement and Data Analysis of Anisotropic Materials. References. 7 Data Analysis Examples. 7.1 Insulators. 7.2 Semiconductors. 7.3 Metals/Semiconductors. 7.4 Organic Materials/Biomaterials. 7.5 Anisotropic Materials. References. 8 Real-Time Monitoring by Spectroscopic Ellipsometry. 8.1 Data Analysis in Real-Time Monitoring. 8.2 Observation of Thin-Film Growth by Real-Time Monitoring. 8.3 Process Control by Real-Time Monitoring. References. Appendices. 1 Trigonometric Functions. 2 Definitions of Optical Constants. 3 Maxwell's Equations for Conductors. 4 Jones-Mueller Matrix Conversion. 5 Kramers-Kronig Relations. Index.
Some aspects of the destruction of lysine under conditions of acid and enzymic hydrolysis of protein materials containing carbohydrates.
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