High numerical aperture Hartmann wave front sensor for extreme ultraviolet spectral range

Area of Science:

• Optics and Photonics
• Extreme Ultraviolet (EUV) Technology
• Metrology and Measurement Science

Background:

• Accurate wavefront measurement is critical for characterizing and optimizing optical systems.
• Existing wavefront sensors often lack suitability for the extreme ultraviolet (EUV) spectral range.
• The development of advanced EUV sources and optics necessitates precise metrology tools.

Purpose of the Study:

• To present a novel Hartmann wavefront sensor specifically designed for the extreme ultraviolet (EUV) spectral range.
• To demonstrate the sensor's capability for high-accuracy wavefront measurements in the 10 nm to 45 nm regime.
• To highlight the sensor's suitability for in situ applications with modern EUV sources and optics.

Main Methods:

• Development of a compact Hartmann wavefront sensor with a numerical aperture (NA) of 0.15.
• Calibration of the sensor using a gas high harmonic generation (HHG) based EUV radiation source.
• Validation of sensor accuracy through calibration and simulation data.

Main Results:

• The novel Hartmann wavefront sensor operates effectively in the EUV spectral range (10-45 nm).
• Calibration and simulations demonstrate a high accuracy exceeding λ/39 root mean square (rms) at λ=32 nm.
• The sensor is compact, high-vacuum compatible, and designed for in situ measurements.

Conclusions:

• The presented Hartmann wavefront sensor represents a significant advancement for EUV metrology.
• Its high accuracy and in situ capabilities make it ideal for characterizing novel EUV sources and high-NA optics.
• This sensor facilitates broader applications and advancements in the field of EUV lithography and microscopy.