Patent ID: 8268516

Claim:
A method for repairing phase shift masks for photolithography, the method comprising: inspecting a phase shift mask for the presence of defects and, if defects are present, i) performing an analysis to determine which of the defects adversely affect imaging properties of the phase shift mask, ii) repairing the defects, iii) analyzing the imaging properties of the repaired phase shift mask and checking adherence to a predefined tolerance criterion, including determining, for each of the defects being repaired, a test quantity as a function of focus and exposure for the defect and at least one other, non-defect site on the phase shift mask in a vicinity of the defect, the tolerance criterion comprising a minimum allowable deviation of the test quantities for defect and non-defect sites, and iv) repeating the two previous steps, ii) and iii) if the imaging properties do not meet the predefined tolerance criterion.