Patent ID: 7709160

Claim:
A method of designing an embedded attenuated phase shift mask or mask blank for use in a lithographic process, the mask or mask blank comprising a halftone stack, the mask or mask blank being suitable for off-axis illumination and/or hyper numerical aperture (NA), the method comprising: selecting mask setting values for the phase shift mask or mask blank and process parameter values for the lithographic process, the process parameter values comprising at least a numerical aperture equal to or larger than about 1, selecting an image performance parameter, performing an aerial image simulation using the selected mask setting values and deriving from the aerial image simulation the corresponding value for the image performance parameter, evaluating the derived image performance parameter value with respect to a predetermined image performance parameter criterion, and if the derived image performance parameter does not fulfill the image performance parameter criterion, adjusting the mask setting values based on the derived image performance parameter and repeating the performing a simulation and the evaluating, wherein adjusting the mask setting values based on the derived image performance parameter comprises adjusting a selected thickness of an absorber and/or phase shift material taking into account said derived performance parameter.