US4583298A
Expired / Lapsed
US
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Auto calibration method suitable for use in electron beam lithography
Assignee: HP Inc
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Filing: 1984-03-07
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Granted: 1986-04-22
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Expires: 2004-03-07
Abstract
Abstract A method of selecting values for parameters in a calibration map used to correct for measurement errors. The locations of points in a grid on an uncalibrated calibration plate are measured for different orientations of the calibration plate. The parameters in the calibration map and the parameters relating the orientations of the calibration plate are determined to minimize the deviation from congruence of the image under the calibration map of the grid in each orientation. The orientations should be related by rigid motions having rotation axes that are separated sufficiently to remove uncertainties in the calibration which arise if the rotation axes are all collinear or nearly collinear.
Inventors
- 👤 Michael R. Raugh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:48
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/002; G01B15/00; H; H01; H01J; H01J37/00; H01J37/30; H01J37/304; H01J37/3045
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
208 words
A method of calibrating measurement values produced by a measuring device, said method being of the type in which a calibration map is used to map measured values into a calibrated coordinate system to correct for distortions in the measurement process, in which the calibration map contains a first set of parameters that are determined by the calibration method and in which the locations of points in a grid on a calibration plate are measured, said method comprising the steps of: (a) orienting the calibration plate in a plurality of different orientations related to one another by the physical values of a second set of parameters, one of said orientations being referred to herein as the reference orientation and the other orientations being referred to herein as non-reference orientations; (b) for each orientation, measuring the locations of the points in the grid; (c) for each orientation, by use of the calibration map, determining the calibrated measured values for each grid point, thereby producing in the calibrated coordinate system an image of the grid for that orientation; (d) selecting numerical values for the first and second sets of parameters to minimize the deviation from congruence with one another of the images of the grid in the calibrated coordinate system.
Claim 2
Independent Claim
208 words
A method of calibrating measurement values produced by a measuring device, said method being of the type in which a calibration map is used to map measured values into a calibrated coordinate system to correct for distortions in the measurement process, in which the calibration map contains a first set of parameters that are determined by the calibration method and in which the locations of points in a grid on a calibration plate are measured, said method comprising the steps of: (a) orienting the calibration plate in a plurality of different orientations related to one another by the physical values of a second set of parameters, one of said orientations being referred to herein as the reference orientation and the other orientations being referred to herein as non-reference orientations; (b) for each orientation, measuring the locations of the points in the grid; (c) for each orientation, by use of the calibration map, determining the calibrated measured values for each grid point, thereby producing in the calibrated coordinate system an image of the grid for that orientation; (d) selecting numerical values for the first and second sets of parameters to minimize the deviation from congruence with one another of the images of the grid in the calibrated coordinate system.
Claim 3
Dependent Claim
26 words
A method as in claim 1 wherein step (a) comprises placing the calibration plate in a plurality of orientations on a stage of the measuring device.
Claim 4
Dependent Claim
32 words
A method as in claim 2 wherein the stage has constant intrinsic curvature, the calibration grid is dimensionally stable and the orientations are related by dimensionally stable motions of the calibration plate.
Claim 5
Dependent Claim
25 words
A method as in claim 3 wherein the stage is substantially planar, the calibration plate is rigid and the orientations are related by rigid motions.
Claim 6
Dependent Claim
38 words
A method as in claim 3 wherein the calibration plate is a polygon and wherein step (a) comprises successively fitting each of the corners of the calibration plate into a corner of a frame mounted on the stage.
Claim 7
Dependent Claim
38 words
A method as in claim 5 wherein the polygon is non-equilateral and wherein the angular size of the corners of the polygon are all equal and are equal to the angular size of said corner of the frame.
Claim 8
Dependent Claim
39 words
A method as in claim 3 wherein the frame is a polygon and wherein step (a) comprises successively fitting the same corner of the calibration plate into each of the corners of a polygonal frame mounted on the stage.
Claim 9
Dependent Claim
41 words
A method as in claim 7 wherein the frame is a non-equilateral polygon and wherein the angular size of the corners of this polygon are each equal and are equal to the angular size of said corner of the calibration plate.
Claim 10
Dependent Claim
34 words
A method as in claim 3 wherein each dimensionally stable motion has a rotation axis and an angle of rotation about that axis and wherein at least two of these rotation axes are distinct.
Claim 11
Dependent Claim
29 words
A method as in claim 1 further comprising after step (d) the step of: (e) performing a numerical simulation of the accuracy of calibration achieved by the calibration map.
Claim 12
Dependent Claim
131 words
A method as in claim 10 wherein step (e) comprises the steps of: (f) determining a distortion map which is substantially equal to the inverse of the calibration map determined by steps (a)-(d); (g) selecting a set of congruent simulation grids in the calibrated coordinate system, at least three of the grids being related by rigid motions having distinct rotation axes; (h) for each point in the grids in step (h), producing simulated measured values, each value being the sum of a random simulated measurement error and the value determined by the distortion map, thereby producing in a space of simulated measured values a set of grids, each of which is the image under the distortion map of a simulation grid, each such image being referred to herein a measured grid:
Claim 13
Dependent Claim
71 words
(i) performing steps (c) and (d) for this set of simulated measured values to produce simulated calibrated measured values thereby producing in the calibrated coordinate system an image of each of the measured grids, these images of the measured grids being referred to as the set of calibrated simulation grids; (j) determining the amount of deviation from congruence of the set of calibrated simulation grids from the set of simulation grids.
Claim 14
Dependent Claim
71 words
(i) performing steps (c) and (d) for this set of simulated measured values to produce simulated calibrated measured values thereby producing in the calibrated coordinate system an image of each of the measured grids, these images of the measured grids being referred to as the set of calibrated simulation grids; (j) determining the amount of deviation from congruence of the set of calibrated simulation grids from the set of simulation grids.
Claim 15
Dependent Claim
35 words
A method as is claim 11 wherein the physical value of a parameter in the second set of parameters substantially minimizes the deviation from congruence (determined in step (j)) as a function of this parameter.
Claim 16
Dependent Claim
38 words
A method as in claim 11 wherein the orientations in step (a) are related to one another by dimensionally stable motions, each of which is characterized by a rotation axis and an angle of rotation about that axis.
Claim 17
Dependent Claim
45 words
A method as in claim 13 wherein, for a given pattern of rotation axes and given rotation angles, the scale of distances between rotation axes in the pattern substantially minimizes the deviation from congruence (determined in step (j)) as a function of this scale parameter.
Claim 18
Dependent Claim
54 words
A method as in claim 12 further comprising a plurality of repetitions of steps (a)-(e) for a range of values of a parameter in the second set of parameters to determine what range of values of this parameter substantially minimizes as a function of this parameter the deviation from congruence (determined in step (j)).
Claim 19
Dependent Claim
81 words
A method as in claim 15 wherein the orientations in step (a) are related to one another by dimensionally stable motions, each of which is characterized by a rotation axis and an angle of rotation about that axis and wherein, for a given pattern of rotation axes and given rotation angles, the scale of distances between rotation axes in the pattern is chosen to substantially minimize the deviation from congruence (determined in step (j)) as a function of this scale parameter.
Claim 20
Dependent Claim
149 words
A method of calibrating measurement values produced by a measuring device, said method being of the type in which a calibration map is used to map measured values into a calibrated coordinate system to correct for distortions in the measurement process and in which the calibration map contains a first set of parameters that are determined by the calibration method, said method comprising the steps of: (k) measuring the locations of points in a grid on a calibration plate, the relative locations of the points in the grid being known by use of the method in claim 1, said calibration map functioning to produce an image of said grid in the calibrated coordinate system; (l) selecting the values of the first set of parameters to minimize in the calibrated coordinate system the deviation from congruence of the image of the measured points with the grid on the calibration plate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-04-21 | 1989-10-21 | 1990-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-21 | 1993-10-21 | 1994-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-21 | 1997-10-21 | 1998-04-22 | $7700.00 | Window Closed / Lapsed |