Method for aligning a mirror of a microlithographic projection exposure apparatus
First Claim
1. A method for aligning a mirror of a microlithographic projection exposure apparatus, wherein the mirror comprises a plurality of mirror segments, said method comprising:
- projecting a beam towards the mirror comprising the plurality of mirror segments;
generating an aerial image from a combination of a first wavefront of a first partial beam reflected at a first mirror segment of the mirror and a second wavefront of a second partial beam reflected at a second mirror segment of the mirror; and
aligning the first mirror segment with the second mirror segment in accordance with an evaluation of the aerial image, wherein distances of the mirror segments from respective predetermined, hypothetical surfaces in a direction of the respective surface normals are less than λ
/10 at each point on the mirror segments, where λ
denotes an operating wavelength of the mirror.
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Abstract
A method for aligning a mirror of a microlithographic projection exposure apparatus, according to one formulation, involves: recording a first partial interferogram between a wave reflected at a first mirror segment (101) and a reference wave reflected at a reference surface (110, 310, 510), recording a second partial interferogram between a wave reflected at a second mirror segment (102) and a reference wave reflected at the reference surface, determining a phase offset between the first partial interferogram and the second partial interferogram, and aligning the first mirror segment and the second mirror segment in relation to one another in accordance with the determined phase offset, so that the distance of the relevant mirror segments (101, 102) from a respective predetermined, hypothetical surface in the direction of the respective surface normal is less than λ/10 at each point on the mirror segments, where λ denotes the operating wavelength of the mirror.
14 Citations
19 Claims
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1. A method for aligning a mirror of a microlithographic projection exposure apparatus, wherein the mirror comprises a plurality of mirror segments, said method comprising:
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projecting a beam towards the mirror comprising the plurality of mirror segments; generating an aerial image from a combination of a first wavefront of a first partial beam reflected at a first mirror segment of the mirror and a second wavefront of a second partial beam reflected at a second mirror segment of the mirror; and aligning the first mirror segment with the second mirror segment in accordance with an evaluation of the aerial image, wherein distances of the mirror segments from respective predetermined, hypothetical surfaces in a direction of the respective surface normals are less than λ
/10 at each point on the mirror segments, where λ
denotes an operating wavelength of the mirror. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for aligning a mirror of a microlithographic projection exposure apparatus, wherein the mirror comprises a plurality of mirror segments, said method comprising:
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projecting a beam towards the mirror comprising the plurality of mirror segments; generating an aerial image from a combination of a first wavefront of a first partial beam reflected at a first mirror segment of the mirror and a second wavefront of a second partial beam reflected at a second mirror segment of the mirror; and aligning the first mirror segment with the second mirror segment in accordance with an evaluation of the aerial image, wherein distances of the mirror segments from respective predetermined, hypothetical surfaces in a direction of the respective surface normals are less than λ
/10 at each point on the mirror segments, where λ
denotes an operating wavelength of the mirror,wherein projecting the beam towards the mirror comprises using electromagnetic radiation at a first wavelength for a pre-aligning and, subsequent to the pre-aligning, using electromagnetic radiation at a second wavelength, which is shorter than the first wavelength for a fine aligning.
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11. A method for aligning a mirror of a microlithographic projection exposure apparatus, wherein the mirror comprises a plurality of mirror segments, said method comprising:
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projecting a beam towards the mirror comprising the plurality of mirror segments; generating an aerial image from a combination of a first wavefront of a first partial beam reflected at a first mirror segment of the mirror and a second wavefront of a second partial beam reflected at a second mirror segment of the mirror; and aligning the first mirror segment with the second mirror segment in accordance with an evaluation of the aerial image, wherein distances of the mirror segments from respective predetermined, hypothetical surfaces in a direction of the respective surface normals are less than λ
/10 at each point on the mirror segments, where λ
denotes an operating wavelength of the mirror,wherein generating the aerial image comprises; arranging a scintillator in an optical path of the first wavefront and the second wavefront to form a scintillated beam; arranging a magnifying imaging optical unit in the beam path of the scintillated beam to form a magnified beam; and arranging a charge coupled device camera in the magnified beam to generate the aerial image. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification