ELIAS III Echelle Spectrometer – 20 fm FWHM Resolution at a Wavelength of 193 nm

LTB Lasertechnik Berlin has delivered the first units of its latest spectrometer generation, ELIAS III, to several lithography laser manufacturers.

The ELIAS III can measure a minimum line width of 20 fm full width at half maximum (FWHM) at a wavelength of 193 nm, corresponding to a spectral resolution of 10 million. To measure such a narrow line width, it is essential to prove the resolution capability and system function of the spectrometer using a laser with a significantly narrower spectral width. For this reason, LTB acquired the first 193 nm “Indigo-DUV” laser from Coherent, with an FWHM of 6 fm, in Europe. Since purchasing such a laser is a significant investment, LTB offers commercial use of this laser in its in-house application laboratory to interested parties.

The ELIAS III series is offered with a spectral resolution of 20 fm FWHM (i.e., 150 MHz or 0.005 cm-1) at 193 nm and 175 fm E95. The internationally accepted definition for characterizing the spectral purity of lithography lasers is to measure the spectral width in which 95% of the energy is contained. Such a measurement is only possible if it can be done with a very high signal-to-noise ratio (typically 20,000, > 40 dB). Compared to Fabry-Perot spectrometers, which can easily measure half-widths in the stated range, it is also possible to quantitatively analyze the foot region and the spectral surroundings.

ELIAS III is the latest patented model in the series of ultra-high-resolution spectrometers developed by LTB in collaboration with the Institute for Spectrochemistry and Applied Spectroscopy (ISAS) Berlin.