Carl Zeiss Sms Ltd.

Peter Kuschnerus

Oliver Kienzle

Axel Zibold

The invention relates to a method for repairing phase shift masks for photolithography in which a phase shift mask is checked for the presence of defects and, if defects are present, (i) an analysis is conducted as to which of the defects negatively affect imaging properties of the phase shift mask, (ii) said defects are improved, (iii) the imaging properties of the improved phase shift mask are analyzed and the maintenance of a predetermined tolerance criterion is checked, and (iv) the two preceding steps (ii) and (iii) are optionally repeated multiple times if the imaging properties do not meet the predetermined tolerance criterion. In such a method, the imaging properties are analyzed in that, for each defect to be improved, a test variable is determined for the defect as a function of focus and illumination, and at least one additional non-defective point on the phase shift mask in the immediate vicinity of the defect is determined, and a minimum allowable deviation between the test variable for the defect and the non-defective point is predetermined as the tolerance criterion.

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Jena, Germany

Peter Kuschnerus