Actinic characterization and modeling of the EUV mask stack

This paper presents a detailed mask stack modeling based on experimental actinic characterization of the EUV mask stack. A dedicated mask has been fabricated with line/space gratings down to 40nm half-pitch (at mask level, i.e., 10nm at wafer). Using the Advanced Light Source facility at LBNL extensive reflectometry and diffractometry have been performed. The experimental reflectivity results through incidence angle and through EUV wavelength enable us to model both the multilayer definition, as well as the absorber definition in the simulator. The effective performance of the calibrated mask stack in the simulator is validated against the experimental diffractometry results through incidence angle. The presented experimental mask stack characterization and modeling allows a better definition of the mask stack in the simulation tools to enhance their predictive and precompensation power.