Xe laser plasma as a radiation source for lithography at wavelengths near 11 nm

For Russian citation (Opticheskii Zhurnal):

Калмыков С.Г., Буторин П.С. Ксеноновая лазерная плазма как источник излучения для литографии на длинах волн вблизи 11 нм // Оптический журнал. 2024. Т. 91. № 6. С. 47–61. http://doi.org/10.17586/1023-5086-2024-91-06-47-61

Kalmykov S.G., Butorin P.S. Xe laser plasma as a radiation source for lithography at wavelengths near 11 nm [in Russian] // Opticheskii Zhurnal. 2024. V. 91. № 6. P. 47–61. http://doi.org/10.17586/1023-5086-2024-91-06-47-61

For citation (Journal of Optical Technology):

Abstract:

Subject of study. Laser plasma excited on a gas-jet Xe target. Goal of the work. Achieving high emissivity of Xe plasma at a wavelength of 11.2 nm, meeting the requirements of industrial lithography. In addition to being clearly applied, the work also has a diagnostic component, the purpose of which was to study the internal structure of the laser plasma and determine its internal parameters: temperature,
concentration and average ion charge. Methodology. The review contains an analysis of works devoted to the complex study of laser plasma with an Xe gas-jet target. During this research, measurement and diagnostic methods were developed and tested: multi-mirror Bragg spectrometry; probing the plasma with infrared laser radiation that creates it; determination of the average ion charge of a nonequilibrium
short-lived laser plasma based on data on the electron impact ionization cross section. Main results. A multi-mirror Bragg spectrometry technique has been developed and tested. With its help, quantitatively calibrated spectra of Xe laser plasma were obtained. An effective regime for irradiating a target with a wide, defocused beam has been found, which has made it possible to obtain a value for the conversion coefficient of laser radiation energy into plasma radiation energy in a narrow wavelength band around 11.2 nm, approximately equal to 4%, which is currently a world record for a plasma of this type. An analytical method for determining the temperature and ion charge of a plasma, based on experimental measurements, has been developed. Practical significance. The conversion of laser
energy into Extreme Ultraviolet radiation with a wavelength of 11.2 nm for laser plasma excited on an Xe gas jet target is sufficient for its use in a high-throughput, industrial lithography process at this wavelength. The use of a simple and “clean” Xe plasma radiation source would avoid a number of problems faced by modern lithography with a wavelength of 13.5 nm and a source with a metal tin target.

Keywords:

laser plasma, xenon, gas-jet target, laser pulse, absorption, Extreme Ultraviolet radiation, Bragg spectrometry, optimization, diagnostic method

Acknowledgements:

this work was carried out in accordance with the State Assignment of Ioffe Institute (№ 0040-2019-0001)

OCIS codes: 120.5240, 260.5210, 260.7200, 300.6170, 300.6190

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