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.
Highlights
Extreme ultraviolet lithography (EUVL) is considered to be the most promising technology for the production of the next-generation of integrated circuits.[1,2,3] The current light source, argon fluoride (ArF) lasers, complies with Moore’s law[4] by utilizing many techniques such as water immersion and multi-patterning.[5]
Ablated oxygen atoms from an oxidized Sn surface reabsorbed more of the generated extreme ultraviolet (EUV) than that compared to a clean tin surface resulting in a lower intensity
To analyze EUVL systems, sufficient protection for the imaging plates (IPs) is highly recommended
Summary
Extreme ultraviolet lithography (EUVL) is considered to be the most promising technology for the production of the next-generation of integrated circuits.[1,2,3] The current light source, argon fluoride (ArF) lasers, complies with Moore’s law[4] by utilizing many techniques such as water immersion and multi-patterning.[5] the limits of these techniques are being reached. To produce the lithographic light, the extreme ultraviolet (EUV) light source utilizes EUV light from laserproduced plasmas (LPPs), which produces highly efficient 13.5 nm EUV.[6] Recently, power of 100 W at the intermediate focus has been obtained through improvements to the entire EUVL system by the use of liquid tin droplets.[7,8]. For EUVL high volume manufacturing (HVM) to be viable, the power at the intermediate focus must be greater than 240 W. Any improvements that could increase the power and cost-efficiency of the system would be welcome.[9] a)Present address: Graduate school of Environmental and Life Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
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