US 11,914,303 B2
Apparatus and method for characterizing a microlithographic mask
Johannes Ruoff, Aalen (DE); Heiko Feldmann, Aalen (DE); Ulrich Matejka, Jena (DE); Thomas Thaler, Jena (DE); Sascha Perlitz, Jena (DE); Shao-Chi Wei, Weimar (DE); Joerg Frederik Blumrich, Jena (DE); and Markus Deguenther, Florstadt (DE)
Assigned to Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed by Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed on Jun. 11, 2021, as Appl. No. 17/345,024.
Claims priority of application No. 10 2020 207 566.2 (DE), filed on Jun. 18, 2020.
Prior Publication US 2021/0397099 A1, Dec. 23, 2021
Int. Cl. G03F 7/20 (2006.01); G03F 7/00 (2006.01); G01N 21/956 (2006.01)
CPC G03F 7/70191 (2013.01) [G01N 21/956 (2013.01); G01N 2021/95676 (2013.01)] 17 Claims
OG exemplary drawing
 
1. An apparatus for characterizing a microlithographic mask, comprising
at least one light source which emits coherent light;
an illumination optical unit which produces a diffraction-limited light spot on the mask from the coherent light of the at least one light source, wherein the illumination optical unit comprises a zone plate;
a scanning device, by use of which it is possible to implement a scanning movement of the diffraction-limited light spot relative to the mask;
a sensor unit; and
an evaluation unit for evaluating the light that is incident on the sensor unit and has come from the mask;
wherein the apparatus comprises:
an output coupling element for coupling out a portion of the coherent light emitted by the at least one light source wherein the output coupling element is formed by a reflecting region of said zone plate; and
an intensity sensor for capturing the intensity of this output coupled portion.