Patent ID: 7094507

Claim:
A method for determining an optimal absorber stack geometry of a lithographic reflection mask comprising a reflection layer and a patterned absorber stack provided on the reflection layer, the absorber stack having a buffer layer and an absorber layer, comprising: a) defining a target pattern for a structure imaged on a substrate by an exposure tool including the lithographic reflection mask to reflect a radiation, the target pattern comprising a critical dimension range of target critical dimension values; b) defining an absorber stack geometry for the target pattern including defining a value of at least one absorber stack parameter, the absorber stack parameter includes a buffer thickness, a buffer sidewall angle, an absorber thickness, an absorber sidewall angle and a lateral absorber stack dimension; c) simulating aerial images of the structure imaged on the substrate for a predetermined range of defocus values; d) evaluating each aerial image by applying a predetermined range of intensity threshold values to determine corresponding critical dimension values of the structure imaged on the substrate; e) comparing the obtained critical dimension values of the structure imaged on the substrate with the critical dimension range of target critical dimension values of the target pattern to determine a process window, wherein the size of the process window is defined by defocus and intensity threshold values corresponding to target critical dimension values; f) defining further absorber stack geometries for the target pattern by varying the value of the absorber stack parameter; g) repeating steps c) to e) for the further absorber stack geometries to determine further process windows; and h) comparing the sizes of the determined process windows corresponding to the defined absorber stack geometries to determine the optimal absorber stack geometry, wherein the optimal absorber stack geometry is identified by the maximum process window size.