Investigation of the interaction of a laser pulse with a preformed Gaussian Sn plume for an extreme ultraviolet lithography source

Abstract

The interaction of a laser pulse with a Sn preplasma formed by a low energy prepulse was investigated for an extreme ultraviolet ͑EUV͒ lithography light source. A much lower ion kinetic energy and nearly the same conversion efficiency from laser to in-band ͑2% bandwidth͒ 13.5 nm EUV light were simultaneously observed as compared with those from the direct interaction with a solid surface. The reason comes from the interaction of the laser pulse with a smooth preplume induced by the prepulse. The density profile of the preplume was measured with time-resolved shadowgraphy and could be fitted with a Gaussian function. The energy of the ions located at the flux peak E p scales with the length of the preplume l s as E p ϰ 1/l s . Laser absorption in the low-density preplume and ion acceleration during plasma expansion are discussed. This result provides a general way to control particle energy from a laser plasma interaction.

Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

“…12,13 Ionized and neutral particle flux causes the sputtering and implantation of the debris species into the ML mirror coating, lowering its reflectivity. 15 Several mitigation schemes have been proposed to improve the lifetime of the ML mirror, for example, using magnetic fields, 16 a gas curtain, 17 low energy prepulses, 18 and mass-limited targets. 19,20 By applying a static magnetic field of 1 T a fivefold reduction in Sn debris deposited on Mo/Si multilayer mirror from a Sn planar target has been demonstrated.…”

Influence of laser pulse duration on extreme ultraviolet and ion emission features from tin plasmas

“…27 Energetic ionized and neutral particle flux cause sputtering and implantation into the ML mirror coating, lowering its reflectivity. 28 Several mitigation schemes have been proposed to improve the lifetime of the ML mirror, for example, using magnetic fields, 29 a gas curtain, 20,30 low energy prepulses, 31 and mass-limited targets. 32,33 We used FC for evaluating the role of pulse width and laser intensity on the ion emission from LPP.…”

Angular ion species distribution in droplet-based laser-produced plasmas

“…This acceleration is due to an electrostatic field that is generated by the nonhomogeneous motion of electrons and ions. 7,[30][31][32][33][34][35][36] It is interesting to consider the simple case of a plasma in a slab with quasi-neutral assumption: the number of ions N i esc that would escape from the slab of a given temperature and number density is given by N i esc /N i ¼ r D /L, where r D is the Debye length of the plasma and L is the plume dimension. 31 For the number density and temperature of the emission dominant region (EDR) and for a laser irradiance of 2 Â 10 11 W/cm 2 , N i esc is on the order 10 À5 N i .…”