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:
- recording a first partial interferogram between a wave reflected at a first mirror segment and a reference wave reflected at a reference surface;
recording a second partial interferogram between a wave reflected at a second mirror segment and a further 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 with the second mirror segment in accordance with the determined phase offset, 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.
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Citations
18 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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recording a first partial interferogram between a wave reflected at a first mirror segment and a reference wave reflected at a reference surface; recording a second partial interferogram between a wave reflected at a second mirror segment and a further 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 with the second mirror segment in accordance with the determined phase offset, 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)
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8. 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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splitting a first wavefront after reflection at a first mirror segment; splitting a second wavefront after reflection at a second mirror segment; interferometrically superposing wavefronts, generated by said splitting of the first wavefront, to generate a first partial interferogram; interferometrically superposing wavefronts, generated by said splitting of the second wavefront, to generate a second partial interferogram; 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. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification