US2008158553A1PendingUtilityA1
Optical measurements of patterned articles
Est. expiryMay 27, 2024(expired)· nominal 20-yr term from priority
G01N 21/95607
55
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Claims
Abstract
A method and system are presented for use in measuring/inspecting a patterned article. Optical measurements are applied to a measurement site on the article by illuminating the measurement site with a plurality of wavelengths at substantially normal incidence of the illuminating light, detecting light returned from the illuminated site, and generating measured data indicative thereof. The measurements are applied to the measurement site through a polarizer rotatable between its different orientations selected from a number of pre-calibrated orientations.
Claims
exact text as granted — not AI-modified1 . A method for use in measuring/inspecting a patterned article, the method comprising applying optical measurements to a measurement site on the article by illuminating the measurement site with a plurality of wavelengths at substantially normal incidence of the illuminating light, detecting light returned from the illuminated site, and generating measured data indicative thereof, wherein the measurements are applied to the measurement site through a polarizer rotatable between its different orientations selected from a number of pre-calibrated orientations;
wherein the measurements applied to the measurement site are carried out with the at least three different orientations of the polarizer selected from the at least four pre-calibrated orientations; wherein said at least three selected polarization orientations include two mutually perpendicular polarizations corresponding to the angular orientations β and (90+β), and at least one intermediate polarization orientation corresponding to the polarization vector orientation in between said mutually perpendicular polarization states.
2 . The method of claim 1 , wherein the intermediate polarizations include that corresponding to a (−45°) angular orientation.
3 . The method of claim 2 , wherein the at least three selected polarization orientations include angular orientations β 1 , β 2 and β 3 spaced from each other by a certain step.
4 . The method of claim 3 , wherein said certain set of angles includes: {0°, 65.2°, 90.4°, 116.9°}.
5 . The method of claim 3 , wherein said certain set of angles includes: {0°, 60°, 90°, 120°}.
6 . The method of claim 2 , wherein the selected polarization orientations include at least one additional intermediate polarization orientation.
7 . The method of claim 6 , wherein the three selected polarization orientations include the polarization angular orientation closest to the given angular orientation of the pattern on the article under measurements with respect to a zero-angle of the polarization orientation.
8 . The method of claim 2 , comprising processing the measured data and determining diffraction efficiencies R TE and R TM for, respectively, linear polarization states of the illuminating light relative to the pattern on the article under measurements, and a phase shift between them, thereby enabling calculation of a diffraction efficiency R(φ) for any angular orientation φ of the polarizer relative to the pattern.
9 . The method of claim 8 , wherein the diffraction efficiency R(φ) is calculated as:
R φ =R TE ·cos 4 φ+R TM ·sin 4 φ+2√{square root over ( R TE ·R TM )}·cos δ·sin 2 φ·cos 2 φ
wherein φ is the angle between the grating and polarizer orientations, R TE and R TM are the measured diffraction efficiencies for said mutually perpendicular polarization orientations, and δ is a phase shift between the diffraction efficiencies R TE and R TM .
10 . The method of claim 9 , comprising processing the measured data to determined measured values of diffraction efficiencies, R meas (φ 1 ), R meas (φ 2 ) and R meas (φ 3 ) for the three different angular orientations β 1 , β 2 and β 3 .
11 . The method of claim 10 , comprising using a predetermined theoretical model based on parameters of the pattern and defining matrix coefficients as follows:
(
R
(
ϕ
1
)
R
(
ϕ
2
)
R
(
ϕ
3
)
)
=
(
cos
4
ϕ
1
sin
4
ϕ
1
sin
2
ϕ
1
cos
2
ϕ
1
cos
4
ϕ
2
sin
4
ϕ
2
sin
2
ϕ
2
cos
2
ϕ
2
cos
4
ϕ
3
sin
4
ϕ
3
sin
2
ϕ
3
cos
2
ϕ
3
)
(
R
TE
R
TM
2
R
TE
R
TM
cos
δ
)
wherein R(φ 1,2,3 ) are the diffraction efficiencies for the angular orientations φ 1,2,3 , to determine theoretical values of R TE , R TM and cos δ.
12 . The method of claim 11 , comprising using the matrix coefficients to transform the theoretical values R TE , T TM and cos δ to theoretical values of diffraction efficiencies R sim (φ 1 ), R sim (φ 2 ) and R sim (φ 3 ).
13 . The method of claim 12 , comprising comparing the measured values R meas (φ 1 ), R meas (φ 2 ) and R meas (φ 3 ) to the corresponding theoretical values R sim (φ 1 ), R sim (φ 2 ) and R sim (φ 3 ), to determine whether they satisfy a matching condition with a pre-defined accuracy.
14 . The method of claim 13 , comprising varying the model parameters, upon detecting that the matching condition is satisfied.
15 . The method of claim 14 , comprising using inverse of the matrix coefficients to transform the measured values R meas (φ 1 ), R meas (φ 2 ) and R meas (φ 3 ) to measured values R meas TE , R meas TM and cos δ meas .
16 . The method of claim 15 , comprising comparing the measured values R meas TE , R meas TM and cos δ meas to the theoretical values of R TE , R TM and cos δ, to determine whether they satisfy a matching condition with a pre-defined accuracy.
17 . The method of claim 16 , comprising varying the model parameters, upon detecting that the matching condition is satisfied.
18 . The method of claim 2 , wherein the pattern is an array of spaced-apart parallel regions.
19 . The method of claim 18 , wherein the pattern acts as a diffractive grating for the illuminating light.
20 . A system for use in measuring/inspecting a patterned article, the system comprising:
an illumination assembly configured and operated for producing illuminating light of a plurality of wavelengths; a detection assembly comprising a spectrometer for receiving light of different wavelengths and generating measured data indicative thereof, a light directing assembly configured for directing the illuminating light onto the article along an axis substantially perpendicular to the article and collecting light returned from the article along said axis and directing the collected light to the detection assembly, the light directing assembly comprising a polarizer assembly operated to be rotatable between its different orientations; and a control unit operable for receiving and processing the measured data, the control unit utilizing calibrated data indicative of an angular orientation (p of the pattern on the article under measurements and at least three pre-calibrated orientations of the polarizer, to thereby select the different polarizer orientations for measurements on each measurement site;
wherein said at least three selected polarization orientations include two mutually perpendicular polarizations corresponding to the angular orientations β and (90+β), and at least one intermediate polarization orientation corresponding to the polarization vector orientation in between said mutually perpendicular polarization states.Join the waitlist — get patent alerts
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