Apparatus and method for the measurement of diffracting structures
DCFirst Claim
1. An apparatus for measuring one or more parameters of a diffracting structure and at least one underlying layer on a sample, said apparatus comprising:
- a radiation source that emits broadband radiation;
a polarizing element, said radiation passing through said polarizing element toward said sample, said radiation being normally incident on and diffracted by said diffracting structure and at least one underlying layer on said sample, a zeroth order diffracted radiation passing through said polarizing element, at least one of said polarizing element and said sample are rotatable to produce a relative rotation between said polarizing element and said diffracting structure;
a spectrograph that detects the intensity of spectral components of said zeroth order diffracted radiation after passing through said polarizing element at a plurality of polarization orientations between said polarizing element and said diffracting structure;
wherein said spectrograph produces a spectrograph signal for said spectral components at a plurality of polarization orientations, said apparatus further comprising a computer system for analyzing said spectrograph signal to determine said one or more parameters of said diffracting structure and at least one underlying layer on said sample, said computer system comprising;
at least one computer connected to said spectrograph to receive said spectrograph signal; and
a computer program executed by said at least one computer, wherein said computer program includes instructions for;
extracting spectral information from said spectrograph signal;
obtaining an optical model simulating said diffracting structure and at least one underlying layer using at least one variable parameter;
obtaining spectral information for said optical model; and
curve fitting said spectral information for said optical model to the extracted spectral information to determine said one or more parameters of said diffracting structure and at least one underlying layer on said sample.
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Abstract
A normal incidence reflectometer includes a rotatable analyzer/polarizer, which permits measurement of a diffracting structure. Relative rotation of the analyzer/polarizer with respect to the diffracting structure permits analysis of the diffracted radiation at multiple polarity orientations. A spectograph detects the intensity of the spectral components at different polarity orientations. Because the normal incidence reflectometer uses normally incident radiation and an analyzer/polarizer that rotates relative to the diffracting structure, or vice-versa, the orientation of the diffracting structure does not affect the accuracy of the measurement. Thus, the sample holding stage may use X, Y, and Z, as well as r-θ type movement and there is no requirement that the polarization orientation of the incident light be aligned with the grating of the diffraction structure. A non-linear multivariate regression process is used to adjust the parameters of an optical model, such as rigorous coupled-wave analysis, to provide a match with the measured data.
98 Citations
16 Claims
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1. An apparatus for measuring one or more parameters of a diffracting structure and at least one underlying layer on a sample, said apparatus comprising:
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a radiation source that emits broadband radiation; a polarizing element, said radiation passing through said polarizing element toward said sample, said radiation being normally incident on and diffracted by said diffracting structure and at least one underlying layer on said sample, a zeroth order diffracted radiation passing through said polarizing element, at least one of said polarizing element and said sample are rotatable to produce a relative rotation between said polarizing element and said diffracting structure; a spectrograph that detects the intensity of spectral components of said zeroth order diffracted radiation after passing through said polarizing element at a plurality of polarization orientations between said polarizing element and said diffracting structure; wherein said spectrograph produces a spectrograph signal for said spectral components at a plurality of polarization orientations, said apparatus further comprising a computer system for analyzing said spectrograph signal to determine said one or more parameters of said diffracting structure and at least one underlying layer on said sample, said computer system comprising; at least one computer connected to said spectrograph to receive said spectrograph signal; and a computer program executed by said at least one computer, wherein said computer program includes instructions for; extracting spectral information from said spectrograph signal; obtaining an optical model simulating said diffracting structure and at least one underlying layer using at least one variable parameter; obtaining spectral information for said optical model; and curve fitting said spectral information for said optical model to the extracted spectral information to determine said one or more parameters of said diffracting structure and at least one underlying layer on said sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of measuring at least one parameter of a diffracting structure and at least one underlying layer, said method comprising:
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(a) passing broadband radiation through a polarizing element to produce polarized radiation; (b) directing said polarized radiation to be normally incident with said diffracting structure, said polarized radiation being diffracted by said diffracting structure and at least one underlying layer; (c) analyzing a zeroth order diffracted radiation with said polarizing element to produce an output beam with a polarity orientation; (d) detecting the intensity of spectral components of said output beam; (e) producing a relative rotation between said polarizing element and said diffracting structure to alter the orientation of said polarized element relative to said diffracting structure and repeating steps a through d; (f) repeating step e for a plurality of orientations of said polarizing element and said diffracting structure; and (g) using the detected intensities of said spectral components of said output beam for a plurality of orientations to determine said at least one parameter of said diffracting structure and at least one underlying layer. - View Dependent Claims (13, 14, 15)
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16. An apparatus for measuring one or more parameters of a diffracting structure and at least one underlying layer on a sample, said apparatus comprising:
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a radiation source that emits broadband radiation, said radiation is normally incident on said diffracting structure; a polarizing element in the beam path of said broadband radiation, wherein said radiation passes through said polarizing element toward said sample, said radiation is diffracted by said diffracting structure on said sample, a zeroth order diffracted radiation passing through said polarizing element, said polarizing element being rotatable to produce a relative rotation between said polarizing element and said diffracting structure; a rotating sample stage for holding said sample with said diffracting structure; a spectrograph that detects the intensity of spectral components of the zeroth order radiation diffracted by said diffracting structure and at least one underlying layer; and a processor for comparing the detected intensity of spectral components of the zeroth order radiation to calculated intensity of spectral components for an optical model of the diffracting structure and at least one underlying layer to determine the one or more parameters of the diffracting structure and at least one underlying layer.
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Specification