The present disclosure provides a photolithography mask. The photolithography mask includes a substrate that contains a low thermal expansion material (LTEM). A multilayer (ML) structure is disposed over the substrate. The ML structure is configured to reflect radiation. The ML structure contains a plurality of interleaving film pairs. Each film pair includes a first film and a second film. The first film and the second film have different material compositions. Each film pair has a respective thickness. For at least a subset of the plurality of the film pairs, the respective thicknesses of the film pairs change randomly along a predefined direction.