New World Record with ELIAS II Echelle Spectrometer

LTB Lasertechnik Berlin achieves a qualitative leap in the development of its unique ultra-high-resolution spectrometer, ELIAS.

With a minimum measurable line width of 60 fm FWHM and 200 fm E95 at a wavelength of 193 nm, or a spectral resolution of more than 3 million, LTB Lasertechnik has made a significant breakthrough in the development of its Echelle spectrometer, ELIAS.

ELIAS II is the latest model in the series of ultra-high-resolution spectrometers. More than 70 systems of its ELIAS series have been delivered worldwide by LTB Lasertechnik Berlin GmbH in the last 2.5 years. ELIAS (Emission Line Analyzing Spectrometer) is the only commercially available spectrometer with such an extremely high resolution.

The main application of these ultra-high-resolution spectrometers is the spectral characterization of excimer lasers used in microlithography at 248 nm, 193 nm, and 157 nm. They indirectly determine the quality of semiconductor circuits produced by optical laser lithography. The quality of the exposure process is determined by the spectral properties of the lasers used and the lens optics. Improving the spectral bandwidth of the laser enables a reduction in structure sizes. With the help of ELIAS, lithography laser manufacturers have succeeded in further developing their light sources, allowing for structure widths of 90 nm to be achieved today.

The spectral resolution of the ELIAS II at 193 nm is 60 fm FWHM (i.e., 500 MHz or 0.016 cm-1) and 200 fm E95. Internationally, the definition for characterizing the spectral purity of a laser line has become the measurement of the spectral width containing 95% of the energy. Such a measurement is only possible when a very high signal-to-noise ratio (typically 20,000, > 40 dB) is achieved.

This makes it possible, compared to Fabry-Perot spectrometers, which can easily measure half-widths in the specified range, to quantitatively analyze the foot region and the spectral surroundings.

However, optical lithography is just one application of the ELIAS series. Due to their sensitivity and high spectral resolution across the entire optical spectral range, the ELIAS spectrometers can also be used in other applications, such as atomic absorption spectroscopy, high-resolution plasma spectroscopy, and laser diode development.