Patent ID: 11914303
Assignee: CARL ZEISS SMT GMBH
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
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.