Extended coupled-wave method for the light absorption of an EUV grid mask

Area of Science:

• Optics and Photonics
• Computational Physics
• Materials Science

Background:

• Rigorous coupled-wave analysis (RCWA) is used for EUV mask simulation.
• RCWA provides complex light amplitude but not direct EUV light absorption.
• Standard algorithms face energy non-conservation issues at material boundaries.

Purpose of the Study:

• To introduce an extended potential transmittance method for EUV mask absorption analysis.
• To address energy non-conservation problems in EUV mask simulations.
• To accurately determine EUV light absorption distribution in grating masks.

Main Methods:

• Developed an extended potential transmittance method.
• Analyzed internal and external electromagnetic field distribution.
• Calculated absorptivity and power changes for different diffraction orders.
• Summed power distribution of all diffracted light for total absorption.

Main Results:

• The extended potential transmittance method accurately describes mask absorption characteristics.
• It accounts for absorptivity of the film system and power changes in diffracted orders.
• The method ensures energy conservation at the absorption material boundary.
• Total grating layer absorption is determined by summing individual diffracted light power distributions.

Conclusions:

• The extended potential transmittance method offers a robust solution for EUV mask absorption simulation.
• It overcomes limitations of traditional RCWA by providing direct absorption data and ensuring energy conservation.
• This method enhances the accuracy of lithography imaging simulation for EUV masks.