Extreme ultraviolet multilayer mirror with near-zero IR reflectance

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Extreme ultraviolet (EUV) lithography requires precise control over radiation wavelengths.
• Standard molybdenum/silicon (Mo/Si) mirrors in EUV systems can be susceptible to unwanted infrared (IR) radiation, particularly from CO2 lasers.
• Suppression of IR radiation is critical for maintaining the efficiency and accuracy of EUV lithography processes.

Purpose of the Study:

• To develop and characterize a novel multilayer mirror with low infrared (IR) reflectance for extreme ultraviolet (EUV) applications.
• To integrate this mirror into an antireflection coating for enhanced performance in EUV lithography tools.
• To demonstrate the effectiveness of the new mirror in suppressing unwanted CO2 laser radiation.

Main Methods:

• Fabrication of a multilayer mirror using alternating layers of diamondlike carbon and silicon.
• Characterization of the mirror's reflectance properties across EUV and IR wavelengths.
• Integration of the multilayer coating into an antireflection structure for IR suppression.

Main Results:

• Achieved up to 49.7% reflectance for extreme ultraviolet (EUV) radiation using the diamondlike carbon/silicon multilayer coating.
• Demonstrated a functional prototype with a combined EUV reflectance of 42.5% and a significantly reduced IR reflectance of 4.4%.
• The developed mirror effectively functions as an antireflection coating for IR radiation at 10.6 µm.

Conclusions:

• The novel diamondlike carbon/silicon multilayer mirror offers a promising solution for IR radiation suppression in EUV lithography.
• This mirror can serve as a superior alternative to standard Mo/Si mirrors, enhancing the efficiency of EUV tools.
• The developed technology provides an efficient method for mitigating interference from unwanted CO2 laser radiation in sensitive EUV applications.