A method for detecting repeating defects in lithography masks based on test substrates which are exposed under varying conditions

A process for the detection of defects (207) on a photolithography mask (200), the method comprising: Determining a permissible range of parameter values ​​of each exposure parameter of an exposure parameter setting when the photolithography mask (200) is used during the production; Performing a plurality of exposure processes with the photolithography mask (200) on the basis of a first exposure parameter setting (E Performing a plurality of exposure processes with the photolithography mask (200) based on a second exposure parameter setting (E and Performing a defect inspection process by means of an inspection device (270) at the plurality of first and second images (261A, 261B) to detect the presence of a repeating defect (262A, 262D, 262F, 262H, 262i, 262L) in at least some of the first and second images (261A, 261B) to estimate.