High-space resolution imaging plate analysis of extreme ultraviolet (EUV) light from tin laser-produced plasmas

Abstract

With the advent of high volume manufacturing capabilities by extreme ultraviolet lithography, constant improvements in light source design and cost-efficiency are required. Currently, light intensity and conversion efficiency (CE) measurments are obtained by charged couple devices, faraday cups etc, but also phoshpor imaging plates (IPs) (BaFBr:Eu). IPs are sensitive to light and high-energy species, which is ideal for studying extreme ultraviolet (EUV) light from laser produced plasmas (LPPs). In this work, we used IPs to observe a large angular distribution (10°-90°). We ablated a tin target by high-energy lasers (1064 nm Nd:YAG, 1010 and 1011 W/cm2) to generate the EUV light. The europium ions in the IP were trapped in a higher energy state from exposure to EUV light and high-energy species. The light intensity was angular dependent; therefore excitation of the IP depends on the angle, and so highly informative about the LPP. We obtained high-space resolution (345 μm, 0.2°) angular distribution and grazing spectrometer (5-20 nm grate) data simultaneously at different target to IP distances (103 mm and 200 mm). Two laser systems and IP types (BAS-TR and BAS-SR) were also compared. The cosine fitting values from the IP data were used to calculate the CE to be 1.6% (SD ± 0.2) at 13.5 nm 2% bandwidth. Finally, a practical assessment of IPs and a damage issue are disclosed.

Electrochemically Synthesized Tin/Lithium Alloy To Convert Laser Light to Extreme Ultraviolet Light

“…The angular distribution is required to obtain CE from laser energy as estimated by eq 2. where E(45), I(45), and LE, are energy at 45°, IP signal at 45°, and irradiated laser energy, respectively. The E(45) value was registered by the calorimeter to be 4.0 × 10 −5 J/sr, according to the same condition as the previous research for tin targets, 40 where the ratio of inband (10−20 nm) per out band (longer than 20 nm) emission was 1:1.8. 10 The CE values for the reference metals were 1.35 and 0.04% for Sn and Li, respectively, for the second shots.…”

“…Before we discuss the material-dependent EUV emission, we will summarize the first and the second shots. In the previous study for Sn, the difference was observed mainly for the first and later shots, the third and fourth shots gave almost the same data as the second, and then, we focus on the second shots in the present study. As for the alloy sample, the thickness is only 2 μm, and the third shot will reach to the Cu substrate.…”

Easy-handling minimum mass laser target scaffold based on sub-millimeter air bubble -An example of laser plasma extreme ultraviolet generation-

“…The EUV spectra were characterized as a strong unresolved transmission array (UTA) emission around 13.5 nm arising from tin transmissions between Sn 8+ and Sn 21+ 35 . The in-band CE at 13.5 nm 2% bandwidth was estimated at 0.8% for the 6-layer SnO 2 microcapsules using a previously described technique 37 . This was lower than the ideal CE (3%) for bulk tin 38 , but comparable to that of bulk tin (1%) at the same laser condition.…”

Gallium–tin alloys as a low melting point liquid metal for repetition-pulse-laser-induced high energy density state toward compact pulse EUV sources

“…Ga : Sn alloys of differing atomic (at%) ratios were synthesized, then characterized using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with X-ray dispersive spectroscopy (EDS). A Nd:YAG laser (1 ns, 2 mJ) was used to generated EUV under similar conditions to previous work, 15 with a grazing incidence spectrometer (GIS). As an example, we show that EUV emission intensity for the Ga : Sn alloy was equal to bulk Sn, depending on the alloy composition.…”