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Method for evaluating complex refractive indicies utilizing IR range ellipsometry

  • US 6,801,312 B1
  • Filed: 06/25/2001
  • Issued: 10/05/2004
  • Est. Priority Date: 12/29/1999
  • Status: Active Grant
First Claim
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1. A method of evaluating mathematical model parameters describing Euler angles and directions, and magnitudes of real and imaginary components, of orthogonally related Kramers-Kroenig consistent complex dielectric functions or refractive indicies in an optically thick material system wherein a beam of electromagnetic radiation reflected from an alignment surface thereof is comprised primarily of components reflecting directly from said alignment surface, said optically thick material system presenting with an optical axis oriented in a selection from the group consisting of:

  • in-plane; and

    out-of-plane;

    with respect to said alignment surface thereof, said optically thick material system being uniaxial in that corresponding real and corresponding imaginary components of at least two orthogonally related optically thick material system characterizing diagonalized tensor;

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    embedded imagecomplex dielectric functions or refractive indicies identified on said diagonal are of equal magnitude, said method comprising, in any functional order, the steps of;

    a) providing an optically thick material system which presents with Kramers-Kroenig consistent complex dielectric functions or refractive indicies and with an optical axis oriented either in-plane or out-of-plane with respect to an alignment surface thereof, said optically thick material system being uniaxial in that corresponding real and corresponding imaginary components of at least two orthogonally related optically thick material system characterizing diagonalized tensor;

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    embedded imagecomplex dielectric functions or refractive indicies are of equal magnitude;

    b) placing said optically thick material system into a system for directing at least one spectroscopic polarized electromagnetic beam(s) of radiation onto said alignment surface at at least one angle(s) of incidence removed from a normal to said alignment surface, said system for directing at least one spectroscopic polarized electromagnetic beam(s) of radiation onto said alignment surface at at least one angle(s) of incidence removed from a normal to said alignment surface comprising a reflection detector system;

    c) selecting at least one spectroscopic polarized electromagnetic beam(s) of radiation to at least partially comprise wavelengths for which said optically thick material system is non-transparent, and causing said at least one beam(s) of spectroscopic polarized electromagnetic radiation to impinge on said alignment surface of said optically thick material system, at at least one angle(s) of incidence removed from a normal to said alignment surface, in plane(s) of incidence which include the locus of said beam of spectroscopic polarized electromagnetic radiation and said normal to said alignment surface, said at least one beam(s) of spectroscopic polarized electromagnetic radiation being caused to reflect from said alignment surface of said optically thick material system and into said reflection detector system;

    d) at said at least one angle(s) of incidence and at at least two rotation angles of said optically thick material system around said normal to the alignment surface thereof, obtaining reflection detector system mediated experimental reflection intensity data as a functions of wavelength and angle of incidence of said at least one beam of spectroscopic polarized electromagnetic radiation onto said optically thick material system alignment surface;

    e) simultaneously providing a mathematical model of said optically thick material system which includes as parameters therein at least;

    real and imaginary components for each of the orthogonally related, Kramers-Kroenig consistent tensor diagonal complex dielectric functions or refractive indicies;

    sufficient rotation about a normal to an alignment surface, and deviation from alignment with said alignment surface angle parameters to define the orientations of the orthogonally related, Kramers-Kroenig consistent tensor diagonal complex dielectric functions or refractive indicies, and orientation of the optical axis, with respect to the alignment surface; and

    Euler angles relating material system angles to a laboratory frame of reference; and

    f) via application of a mathematical regression technique, evaluating parameters in said mathematical model to provide a best-fit to acquired experimental data.

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