Majid Masnavi

Estimation of optimum density and temperature for maximum efficiency of tin ions in Z discharge extreme ultraviolet sources

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the narrow spectrum band of 13.5±0.135 nm. A simplified collisional-radiative model and radiative transfer solution for an isotropic medium were utilized to investigate the wavelength-integrated light outputs in tin (Sn) plasma. Detailed calculations using the Hebrew University-Lawrence Livermore atomic code were employed for determination of necessary atomic data of the Sn4+ to Sn13+ charge states. The result of model is compared with experimental spectra from a Sn-based discharge-produced plasma. The analysis reveals that considerably larger efficiency compared to the so-called efficiency of a black-body radiator is formed for the electron density ≃1018 cm−3. For higher electron density, the spectral efficiency of Sn plasma reduces due to the saturation of resonance transitions.

Potential of discharge-based lithium plasma as an extreme ultraviolet source

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the spectrum band of 13.5±0.135nm. A model was developed to investigate the wavelength-integrated Lyman-α lines light outputs in hydrogen-like lithium ion. The analysis reveals that the commonly observed low conversion efficiency is largely due to a transient nature of Z discharge-based plasma and that a magnetically confined lithium plasma is an efficient EUV source even at low electron temperature. Calculation shows necessary confinement time that raises the conversion efficiency up to half the spectral efficiency.

Laser-plasma source parameters for Kr, Gd, and Tb ions at 6.6 nm

There is increasing interest in extreme-ultraviolet (EUV) laser-based lamps for sub-10-nm lithography operating in the region of 6.6 nm. A collisional-radiative model is developed as a post-processor of a hydrodynamic code to investigate emission from resonance lines in Kr, Gd, and Tb ions under conditions typical for mass-limited EUV sources. The analysis reveals that maximum conversion efficiencies of Kr occur at 5×1010W/cm2, while for Gd and Tb it was ≃0.9%/2πsr for laser intensities of (2−5)×1012W/cm2.

Estimation of the Lyman-α line intensity in a lithium-based discharge-produced plasma source

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the narrow spectrum band of 13.5±0.135 nm. A simplified time-dependent collisional-radiative model and radiative transfer solution were utilized to investigate the wavelength-integrated Lyman-α line light outputs in a hydrogen-like lithium ion. The study reveals in particular that a steady-state or magnetically confined lithium plasma radiates in the desired spectrum band not less than 1 kW in 2π sr even at an ion density region as low as 1017 cm−3.

Effects of Plasma Dynamics on Lasing in Fast Capillary Discharge

The timing, intensity, and pulse width of lasing signals in fast capillary discharge plasma at a strong 2p53p–2p53s transition of Ne-like Ar are experimentally investigated. To clarify the lasing mechanism, the results are compared with those obtained by numerical calculation using a one-dimensional magneto-hydrodynamics (MHD) simulation code. The comparison indicates that the lasing occurs when a cylindrically imploding shock wave arrives at the axis of the capillary and it depends not only on the electron density and temperature but also strongly on the effects of time-varying refraction and the opacity of the pinching plasma.

Effect of nonequilibrium ionization process on gain of neon-like argon x-ray laser

In connection with fast plasma heating in capillary discharges, transient ionizationeffect on the gain of J=0→1 transition (λ=46.9  nm ) in optically thin neon (Ne)-like argon (Ar IX) x-ray laser has been theoretically investigated using the reduced time-dependent collisional–radiative model. Results indicate that the gain value at nonequilibrium ionization regime is significantly affected by the relaxation process of different ionization states, and fast heating enables us to obtain higher gain compared with the steady-state plasma.

Approach to optimize conversion efficiency of discharge-pumped plasma extreme ultraviolet sources

The possibility of enhancing the conversion efficiency of a capillary-discharged xenon plasma via a current step is theoretically demonstrated using a simplified model. The current step is shown to exert a significant effect on the plasma dynamics in capillary discharge extreme ultraviolet sources. In particular, the pinching phase can be maintained at a quasi-steady-state by the current control, which prolongs the emission period of radiating plasma.

Characteristics of Extreme Ultraviolet Radiation Conversion Efficiency of Xenon Plasma

The characteristics of the plasma conversion efficiency of 4d75p?4d8 transitions of xenon have been theoretically investigated using the quasi-steady-state collisional radiative model. Results indicate that a large conversion efficiency is achieved for electron densities between 1018 and 1019 cm-3. In relation to rapid plasma heating in capillary discharges, the influence of nonequilibrium ionization on the conversion efficiency has been investigated. The study clearly shows that the ionization state distribution is a function of the history of plasma evolution, and a rapid heating process under appropriate plasma conditions allows us to obtain higher conversion efficiency values compared with the steady-state calculations.

Influence of opacity on gain coefficients in static, and fast moving neon-like krypton plasmas

X-ray laser gains and the level populations in collisionally pumped neon (Ne)-like krypton (Kr XXVII) ions have been investigated considering 27 levels of the 2p6, 2p5 3s, 2p5 3p, and 2p5 3d configurations in fast moving cylindrical plasma. Effects of opacity of the 3d 1P1→2p6 1S0, 3d 3D1→2p6 1S0, 3d 3P1→2p6 1S0, 3s 3P1→2p6 1S0, and 3s 1P1→2p6 1S0 transitions on the gain coefficients are considered using escape probability factors in both the static, and dynamic plasmas under the Sobolev approximation, that includes effect of the large velocity gradient. Results indicate that the gain values are significantly affected by plasma opacity, and the velocity gradient allows us to obtain a broader gain region in dense plasmas.

Simulation of particle velocity in a laser-produced tin plasma extreme ultraviolet source

In connection with fast heating in a laser produced plasma (LPP) extreme ultraviolet (EUV) source, the superheating behavior of bulk tin (Sn) at high heating rates is investigated. A constant temperature and pressure molecular dynamics simulation using modified Lennard-Jones and Coulomb potentials suitable for studying the liquid structure of Sn is employed in order to derive the caloric curves of the solid and liquid phases. The results have shown transient effects on the phase transitions. Superheating is observed during the melting and vaporizing processes. The velocity distribution of Sn particles against typical laser fluence in a LPP EUV light source has been numerically investigated using a simplified method including a one-dimensional, two-temperature, molecular dynamics, and steady-state ionization model. In the framework of our model, it was found that ejected Sn particles have a maximum velocity on the order of 10 to 40 km/s in plasma created using a nanosecond pre-pulse neodymium-doped yttrium...