Optimization of a gas discharge plasma source for extreme ultraviolet interference lithography at a wavelength of 11 nm

Abstract

In this work, we report about the optimization of the spectral emission characteristic of a gas discharge plasma source for high-resolution extreme ultraviolet (EUV) interference lithography based on achromatic Talbot self-imaging. The working parameters of the source are optimized to achieve a required narrowband emission spectrum and to fulfill the necessary coherence and intensity requirements. The intense 4f-4d transitions around 11 nm in a highly ionized (Xe8+-Xe12+) xenon plasma are chosen to provide the working wavelength. This allows us to increase the available radiation intensity in comparison with an in-band EUV xenon emission at 13.5 nm and opens up the possibility to strongly suppress the influence of the 5p-4d transitions at wavelengths between 12 and 16 nm utilizing a significant difference in conditions for optical thickness between 4f-4d and 5p-4d transitions. The effect is achieved by using the admixture of argon to the pinch plasma, which allows keeping the plasma parameters approximately constant while, at the same time, reducing the density of xenon emitters. It is demonstrated that with this approach it is possible to achieve a high intensity 11 nm EUV radiation with a bandwidth of 3%-4% without the use of multilayer mirrors or other additional spectral filters in the vicinity of the working wavelength. The achieved radiation parameters are sufficient for high-performance interference lithography based on the achromatic Talbot effect

Generation of circularly polarized radiation from a compact plasma-based extreme ultraviolet light source for tabletop X-ray magnetic circular dichroism studies

“…For our measurements, we employed a gas-discharge plasma EUV light source developed at the Fraunhofer Institute for Laser Technology [18][19][20] and specifically designed for water window operation (280 eV-530 eV). In our experiments, the source parameters were 3.5 kV discharge voltage, 2 μF total capacity and 20 Hz pulse repetition rate.…”

“…[18][19][20] The multiply ionized atoms, in our case oxygen and nitrogen ions, emit narrowbandwidth spectral lines ( E/E = 10 −3 −10 −5 , where E is the photon energy) in the photon energy range between vacuum ultraviolet and soft X-rays. We optimized the EUV light source for operation above 50 eV photon energy.…”

Observations of soft X-ray emission and plasma dynamics of a compact capillary discharge operated in xenon

“…It has also been reported that the peak at 110 Å becomes dominant when a buffer gas is added to the plasma. 25 While only Xe XI is important at 135 Å , many higher stages of xenon strongly emit in the UTA.…”

Особенности экспериментальных спектров лазерной плазмы с плотной Xe газоструйной мишенью в дальнем ультрафиолетовом диапазоне

“…Хотя степень разбавления опре-деляется по давлениям газов перед соплом и соотношение атомар-ных концентраций в потоке точно неизвестно, полученный эффект очевиден и требует объяснения. Идея использования смеси Ar+Xe была предложена впервые в работе [13] для источника EUV-излучения на основе электродного плазменного фокуса. По мнению ее авторов, добавка Ar должна усиливать излучение Xe на длине волны λ = 11.2 nm и подавлять излучение с λ = 13.5 nm из-за специфической эволюции оптической толщины плазмы при разбавлении.…”