Angular and energy distribution of Sn ion debris ejected from a laser-produced plasma source, for laser power densities in the range suitable for extreme ultraviolet lithography

Abstract

In this paper, experimental results are presented for the spatial and energy distributions of charge-discriminated Sn ions ejected from laser-produced plasmas. The plasmas were formed on solid, planar Sn targets, irradiated with a Nd:YAG laser. Ions were investigated using a calibrated electrostatic sector analyzer, scanning an energy-to-charge ratio range of 0.22 to 2.2 keV/e for emission angles between 20 and 80 degrees relative to target normal. Results were obtained for three laser power densities, in the region suitable for inducing significant extreme ultraviolet emission, of the order 1.5–8.1 × 1011 W/cm2. The fully differentiated data were found to be well characterized by Gaussian fits, which allowed trends in the emission profiles to be readily quantified. Ions of set energy and charge were observed to possess a preferential angle of emission, the superposition of which yields a physical basis for the total angular emission observed previously and in this work. The experimental results obtained have been related to physical processes within the plasma that influence the energy and angle of ejection of ions from laser produced plasmas.

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

“…5 The distribution of the ions from the slab target shows a similar decay with the angle for all of the measured ion species. Charge states up to Sn 5þ are found in the slab target results, as the condition was in high vacuum.…”

“…The angular and kinetic energy distributions of ions from LPPs generated in high vacuum were extensively studied for slab targets of tin, 5 and for other materials. [6][7][8][9][10] The effects of the wavelength on the plasma dynamics from tin slab targets were mainly studied with tin slab targets mainly comparing Nd:YAG and CO 2 lasers.…”

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

“…Regardless of the laser pulse width used for excitation, the ion fluence increased with increasing laser energy. O'Connor et al 23 noticed similar effects at a fixed laser width and their studies showed both the number and the energy of ions increased with applied laser energy.…”

“…22 It was also shown that LPPs exhibit preferential emission close to target normal; the energy of the ions emitted close to the target normal were also higher than that of ions emitted at larger angles. 23 Higashiguchi et al 24 demonstrated suppression of suprathermal ions from a colloidal microjet target plasma containing tin-dioxide (SnO 2 ) nanoparticles irradiated by double laser pulses. As a result, the peak energy of the singly ionized tin ions was reduced from 9 to 3 keV.…”

Numerical Modeling of the Photothermal Processing for Bubble Forming around Nanowire in a Liquid

“…The nanowire is illuminated by a TM polarized laser pulse at wavelength λ = 1050 nm of complex permittivity ϵ r (TiO 2 ) 1050 = 5.4600 + j 0.00148 with a power density per area units P S = 1.75 × 10 12  W/m 2 [24, 25]. The materials of the system are considered isotropic and homogeneous.…”