METHOD FOR PRODUCING A MIRROR SUBSTRATE BLANK FROM TITANIUM-DOPED SILICA GLASS FOR EUV LITHOGRAPHY AND SYSTEM FOR DETERMINING THE POSITION OF DEFECTS IN A BLANK

摘要

The invention relates to a method for producing a mirror substrate blank made from titanium-doped silica glass for EUV lithography, having a thickness of at least 40 millimeters, having the following method steps: • a) face grinding of the surface of the blank • b) identifying data on defects in a surface layer of the blank, wherein b1) light penetrates the blank at a predetermined angle of incidence a of less than 90° at a location on the flat surface of the blank, b2) the light scatters on a defect in the blank and b3) the scattered light is detected at a distance x from the penetration location on the surface of the blank by a light detection element arranged perpendicularly thereabove; • c) determining the position of the defect in the surface layer based on the data obtained during method step b) • d) partial or complete removal of the surface layer in consideration of the position determination according to method step c) and forming the mirror substrate blank.