Measurements of the absolute intensities of spectral lines of Kr, Ar, and O ions in the wavelength range of 10 – 18 nm under pulsed laser excitation

Abstract

We have measured the absolute intensities of the spectral lines of Kr, Ar, and O ions (CO2 gas), which are of interest for reflectometry, microscopy, and lithography in the wavelength range of 10 – 18 nm. We have used pulsed excitation by an Nd : YAG laser with an output wavelength λ = 1064 nm, a pulse energy of 0.8 J, a pulse duration of 5.2 ns and a pulse repetition rate of 10 Hz. The targets are formed during gas outflow through a pulsed supersonic conical nozzle for an inlet gas pressure of 3.5 bar. A spectrometer based on X-ray multilayer mirrors and its calibration procedure are described in detail. The absolute intensities of the spectral lines of Kr IX (λ = 11.5 nm; number of photons: N = 9.3 × 1012 photons pulse−1), Ar VIII (λ = 13.84 nm, N = 3 × 1012 photons pulse−1), and O VI (λ = 12.98 nm, N = 5.17 × 1012 photons pulse−1). The results are compared with the data obtained for Xe ions under the same experimental conditions at the same wavelengths.

EUV Radiation in the Range of 10–20 nm from Liquid Spray Targets Containing O, Cl, Br and I Atoms under Pulsed Laser Excitation

“…When alcohol targets are excited, EUV radiation is emitted by oxygen ions O-V and O-VI in the spectral range under study. Oxygen spectra were also obtained and studied using a CO 2 gas jet target [12]. In [12], the absolute value of the emission intensity of the oxygen ion O-VI at a wavelength of 12.98 nm was calculated to be 5.2 × 10 12 ph/pulse.…”

“…Oxygen spectra were also obtained and studied using a CO 2 gas jet target [12]. In [12], the absolute value of the emission intensity of the oxygen ion O-VI at a wavelength of 12.98 nm was calculated to be 5.2 × 10 12 ph/pulse. The absolute value of the radiation intensity at a wavelength of 12.98 nm (see Table 2) obtained in this work when using methyl alcohol as a target exceeds the value obtained with a gas jet target.…”

“…The method for determining the energy and number of photons emitted in a particular spectral band by a laser spark is described in [12]. For the experiments directly carried out in this work, the energy and number of photons were calculated using the following formulas:…”

“…A silicon photodiode with a sensitivity δ = 0.25 C/J was used as a soft X-ray radiation detector [11]. The operating principles, design, and properties of the installation are described in more detail in [12].…”

Thin film Al targets for a laser-plasma source of extreme ultraviolet radiation

“…Experiments were carried out on the installation [5] when the target is excited by an Nd : YaG laser with the following characteristics: wavelength 1064 nm; pulse energy 0.8 J; pulse duration 5.2 ns; pulse repetition frequency 10 Hz; focusing spot diameter 66 µm. Spectrometric measurements were performed on a spectrometer based on multilayer X-ray mirrors of normal incidence [6]. The curve of the spectral sensitivity of the device, determined by the bandwidth of the absorption filters, the spectral dependence of the reflection coefficient of the X-ray mirror and the spectral sensitivity of the EUV radiation detector is shown in Fig.…”