Patent Number: 
Section: claims

1. A method for analyzing a defect of a photolithographic mask for an extreme ultraviolet (EUV) wavelength range (EUV mask), the method comprising:a. generating at least one focus stack relating to the defect using an EUV mask inspection tool, wherein the at least one focus stack comprises an image recorded in a focus plane, at least one image recorded above the focal plane, and at least one image recorded below the focal plane;b. determining a surface configuration of the EUV mask at a position of the defect;c. providing model structures having the determined surface configuration which have different phase errors and generating the respective focus stacks; andd. determining a three dimensional error structure of the EUV mask defect by comparing the at least one generated focus stack of the defect and the generated focus stacks of the model structures. 2. The method of claim 1, further comprising applying different repairing methods to the three dimensional error structure and simulating respective focus stacks in order to determine an optimal repairing method. 3. The method of claim 2, further comprising applying the optimal repairing method to the defective position. 4. The method of claim 2, wherein the repairing method comprises at least partially removing the multilayer structure, in particular drilling at least one hole into the multilayer structure. 5. The method of claim 2, wherein the repairing method comprises locally compacting and/or expanding the multilayer structure and/or a substrate of the EUV mask by locally focusing femtosecond laser pulses into the EUV mask. 6. The method of claim 1, wherein the model structures comprise an absorbing pattern structure on a surface of the EUV mask. 7. The method of claim 6, further comprising providing the absorbing pattern structure from EUV mask design data and/or from a recording of at least one image. 8. The method of claim 1, further comprising using a repairing method correcting the three dimensional error structure, so that a resulting multilayer structure is at least approximately corrected to an ideal multilayer structure. 9. The method of claim 8, further comprising applying the repairing method directly onto the defective position of the EUV mask. 10. An inspection microscope for photolithographic masks in the extreme ultraviolet wavelength range adapted to:a. generate at least one focus stack relating to the defect using an EUV mask inspection tool, wherein the at least one focus stack comprises an image recorded in a focus plane and at least one image recorded above the focal plane and at least one image recorded below the focal plane;b. determine a surface configuration of the EUV mask at a position of the defect;c. provide model structures having the determined surface configuration which have different phase errors and generating the respective focus stacks; andd. determining a three dimensional error structure of the EUV mask defect by comparing the at least one generated focus stack of the defect and the generated focus stacks of the model structures.