Patent ID: 6441902
Filing Date: 2002-08-27
Classification: G01N

Abstract:
A method of determining values for anisotropic refractive indices nx,ny and nz in orthogonally related directions in a sample system comprising, in any functional order, the steps of:a) providing a system selected from the group consisting of: an ellipsometer; a polarimeter; and a spectrophotometer; said system being comprised of at least selections 1, 3, 5, 6, and 9, from the group consisting of:1) a source of a beam of electromagnetic radiation; 2) a polarizer; 3) a stage for supporting a sample system; 4) an analyzer; 5) a reflection detector; 6) a transmission detector; 7) a compensator at some point between said polarizer and analyzer; 8) a modulation element at some point between said polarizer and analyzer; 9) a computational means which is programmed with a mathematical model for said sample system, said mathematical model serving to relate indices of refraction, thickness and optical axis direction over a range of at least one member of the group consisting of: wavelength; â€œPâ€  plane angle-of-incidence of an investigating polarized beam of electromagnetic radiation to an alignment surface of said material system; and sample system rotation angle about a perpendicular to an alignment surface thereof; which computational means includes a routine for fitting numbers to said mathematical model parameters in view of experimental data;said method further comprising practicing steps b, c, d, and e in any functional order, said steps b, c, d, and e being:b) providing, and determining the thickness of, a sample system having two essentially in-plane (nx) (ny) orthogonal indices of refraction in an alignment surface thereof and a third (nz) index of refraction which projects essentially perpendicular to said alignment surface; c) determining a range of wavelengths for which said sample system is essentially transparent; d) placing said sample system on the stage for supporting a sample system so that said alignment surface thereof is accessible by a beam of electromagnetic radiation originating from said source of a beam of electromagnetic radiation; e) determining the precise orientation of the third index of refraction which projects essentially perpendicular to said alignment surface thereof; said method further comprising:f) causing a spectroscopic beam of electromagnetic radiation originating from said source of a beam of electromagnetic radiation, which spectroscopic beam of electromagnetic radiation is comprised of a plurality of wavelengths for which said sample system is essentially transparent, to approach said alignment surface of said sample system along a locus which is essentially co-incident with the orientation of the third index of refraction which projects essentially perpendicular to said alignment surface, at least partially transmit through said sample system and enter said transmission detector to the end that a one-dimensional data set as a function of wavelength is acquired; g) applying said computational means which is programmed with a mathematical model for said sample system to said step f results in view of results from practice of previous steps, to the end that a value for the difference between the in-plane (&Dgr;nxy) indices of refraction and the Euler angle orientations of said essentially in-plane orthogonal (nx) (ny) indices of refraction are determined; h) causing a beam of electromagnetic radiation originating from said source of a beam of electromagnetic radiation, which beam of electromagnetic radiation is comprised of at least one wavelength, to approach said alignment surface of said sample system along a plurality of near normal angles-of-incidence to said sample system alignment surface, interact with said sample system and enter at least one selection from the group consisting of: said reflection detector; and said transmission detector; to the end that a one dimensional data set as a function of angle-of-incidence is acquired;i) applying said computational means which is programmed with a mathematical model for said sample system to said step h results in view of results from practice of previous steps to the end that a value for the difference between at least one out-of-plane combination of indices of refraction selected from the group consisting of: (&Dgr;nxz); and(&Dgr;nyx); andis determined;j) causing a beam of electromagnetic radiation originating from said source of a beam of electromagnetic radiation, which beam of electromagnetic radiation is comprised of at least one wavelength, to approach said alignment surface of said sample system along a plurality of angles-of-incidence at near the Brewster condition to said sample system alignment surface, interact with said sample system and enter at least one selection from the group consisting of: said reflection detector; and said transmission detector; to the end that data as a function of angle-of-incidence is acquired;k) applying said computational means which is programmed with a mathematical model for said sample system to said step j results in view of results from practice of previous steps to the end that an absolute value for at least one index of refraction selected from the group consisting of: â€ƒ(nx);(ny); (nz); is directly determined;said method optionally further comprising steps 1 and m, said steps 1 and m being:1) causing a beam of spectroscopic electromagnetic radiation originating from said source of a beam of electromagnetic radiation to approach said alignment surface of said sample system along a plurality of angles-of-incidence to said sample system alignment surface, and enter at least one selection from the group consisting of: said transmission detector; and said reflection detector; to the end that data as a function of wavelength and angle-of-incidence is acquired; andm) applying said computational means which is programmed with a mathematical model for said sample system to the end that dispersion data for at least one index of refraction selected from the group consisting of: (nx); (ny); (nz); is determined.