Lithographic apparatus and method
First Claim
1. A method of measuring aberration in a lithographic apparatus, the method comprising:
- modulating a radiation beam using an array of individually controllable elements;
projecting the modulated radiation beam using a projection system;
detecting the projected radiation using a moveable sensor; and
measuring aberration in the detected radiation beam,wherein a pattern is provided on the array of individually controllable elements to modulate the radiation beam, wherein the pattern has a repeating structure and is formed from a plurality of features, wherein the plurality of features are dimensioned to generate first order diffraction of the radiation beam that substantially fills the pupil of the projection system, and wherein the moveable sensor steps through and captures an image of an interference pattern in the radiation projected by the projection system, captures an intensity of the image as a function of a stepped distance per step, determines a phase of a first harmonic of the intensity as a function of stepped distance and determines aberrations in the lithographic apparatus based on the phase of the first harmonic.
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Abstract
Systems and methods are provided for measuring aberration in a lithographic apparatus. A radiation beam is modulated using an array of individually controllable elements, and the modulated beam is projected using a projection system. A pattern is provided on the array of individually controllable elements to modulate the radiation beam, and the pattern comprises a repeating structure that is formed from a plurality of features that are dimensioned such that first order diffraction of the radiation beam substantially fills the pupil of the projection system. A sensor detects the projected radiation and measures interference in the radiation projected by the projection system. Aberration in the detected radiation beam is then measured.
48 Citations
19 Claims
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1. A method of measuring aberration in a lithographic apparatus, the method comprising:
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modulating a radiation beam using an array of individually controllable elements; projecting the modulated radiation beam using a projection system; detecting the projected radiation using a moveable sensor; and measuring aberration in the detected radiation beam, wherein a pattern is provided on the array of individually controllable elements to modulate the radiation beam, wherein the pattern has a repeating structure and is formed from a plurality of features, wherein the plurality of features are dimensioned to generate first order diffraction of the radiation beam that substantially fills the pupil of the projection system, and wherein the moveable sensor steps through and captures an image of an interference pattern in the radiation projected by the projection system, captures an intensity of the image as a function of a stepped distance per step, determines a phase of a first harmonic of the intensity as a function of stepped distance and determines aberrations in the lithographic apparatus based on the phase of the first harmonic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A lithographic apparatus comprising:
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an array of individually controllable elements configured to modulate a beam of radiation; a projection system configured to project the modulated beam of radiation; a moveable sensor arranged to detect radiation projected by the projection system; and a controller arranged to provide a pattern on the array of individually controllable elements; wherein the pattern has a repeating structure and is formed from a plurality of features, wherein the plurality of features are dimensioned to generate first order diffraction of the radiation beam that substantially fills the pupil of the projection system, and wherein the moveable sensor is arranged to step through and captures an image of an interference pattern in the radiation projected by the projection system, captures an intensity of the image as a function of a stepped distance per step, determines a phase of a first harmonic of the intensity as a function of stepped distance and determines aberrations in the lithographic apparatus based on the phase of the first harmonic. - View Dependent Claims (18, 19)
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Specification