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Method for aligning a mirror of a microlithographic projection exposure apparatus

  • US 10,359,703 B2
  • Filed: 10/15/2018
  • Issued: 07/23/2019
  • Est. Priority Date: 04/04/2014
  • Status: Active Grant
First Claim
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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:

  • 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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