US 12,111,578 B2
Mirror for an illumination optical unit of a projection exposure apparatus comprising a spectral filter in the form of a grating structure and method for producing a spectral filter in the form of a grating structure on a mirror
Christof Jalics, Heidenheim (DE); Fabian Schuster, Bad Buchau (DE); Holger Kierey, Aalen (DE); Andreas Sandner, Aalen (DE); and Tobias Meisch, Essingen (DE)
Assigned to Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed by Carl Zeiss SMT GmbH, Oberkochen (DE)
Filed on May 11, 2021, as Appl. No. 17/317,417.
Application 17/317,417 is a continuation of application No. PCT/EP2019/082407, filed on Nov. 25, 2019.
Claims priority of application No. 102018220629.5 (DE), filed on Nov. 29, 2018.
Prior Publication US 2021/0263423 A1, Aug. 26, 2021
Int. Cl. G03F 7/00 (2006.01); G02B 5/08 (2006.01); G02B 5/18 (2006.01)
CPC G03F 7/70166 (2013.01) [G02B 5/0891 (2013.01); G02B 5/1861 (2013.01); G03F 7/70191 (2013.01); G03F 7/702 (2013.01)] 24 Claims
OG exemplary drawing
 
17. A method, comprising:
structuring a structuring layer applied on a substrate of a mirror body; and
structuring the substrate of the mirror body,
wherein structuring the substrate of the mirror body comprises at least one member selected from the group consisting of:
etching with an etching angle in the range of 0° to 60°;
etching, wherein the structuring layer and the substrate of the mirror body have different etching rates; and
etching, wherein the structuring layer is provided with a sidewall steepness in the range of 10° to 90° during the structuring; and
applying a closed protective layer on the substrate,
wherein:
the grating structure comprises a plurality of grating ridges;
for each grating ridge, the grating ridges comprises a front side and sidewalls;
for each of at least some pairs of adjacent grating ridges:
a groove comprising a bottom is between the adjacent grating ridges;
a depth of the groove is a distance between the bottom and the adjacent grating ridges; and
the depth of the groove is configured to mask out infrared radiation; and
the grating structure has a maximum edge steepness in the range of 15° to 60°.