Al/Mo/SiC multilayer diffraction gratings with broadband efficiency in the extreme ultraviolet

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Extreme ultraviolet (EUV) lithography requires efficient optical coatings.
• Multilayer mirrors are crucial for EUV applications, but broadband efficiency remains a challenge.
• Optimizing multilayer structures on gratings is key to enhancing EUV optical performance.

Purpose of the Study:

• To optimize Al/Mo/SiC periodic and aperiodic multilayers for high groove density gratings.
• To investigate the impact of multilayer deposition on grating efficiency in the EUV spectrum.
• To develop and validate models for predicting EUV diffraction efficiency of multilayer gratings.

Main Methods:

• Deposition of Al/Mo/SiC periodic and aperiodic multilayers on high groove density gratings.
• Measurement of grating efficiencies using monochromatic synchrotron radiation at various incident angles (5° and 45°).
• Comparison of experimental data with rigorous coupled-wave analysis (RCWA) simulations based on material characterization.

Main Results:

• Demonstrated broadband efficiency in the EUV range (17-31 nm) for both periodic and aperiodic multilayer gratings.
• Showcased the influence of the number of deposited periods on the grating's trapezoidal profile and EUV diffraction efficiency.
• Achieved unprecedented broadband diffraction efficiency using Al/Mo/SiC aperiodic multilayer gratings.

Conclusions:

• The number of periods in periodic multilayer gratings can be adjusted to balance peak efficiency and bandwidth.
• Aperiodic multilayer gratings offer a promising route to achieving superior broadband efficiency in EUV applications.
• The developed models accurately predict the performance of multilayer gratings, aiding future optical design.