EUV application

Plasma EUV source and electron beam (EB) are considered as the candidates for the next generation lithography to achieve the 45nm line and space. The wavelength of this next generation EUV source should be 13.5 nm. Such EUV sources have been investigated thoroughly in the world. Plasma EUV sources are promising, but the required power has not yet been achieved since the projection exposure system requires many mirrors. Also there are problems debris which causes the mirror surfaces and vacuum to deteriorate.

Transition radiation (TR) is emitted when a relativistic particle passes through the interface between two different materials^[1,2]. The main sources of TR are electron synchrotrons (SR), in which TR is emitted by passing relativistic electrons through targets (TR targets) of the appropriate material.

A MIRRORCLE type synchrotron^[3] emitting transition radiation (TR) represents an important source of soft X-ray and extreme ultraviolet (EUV) radiation. Such radiation can be used for performing deep-edge lithography for the LIGA process micro-fabrication^[4], X-ray lithography (XRL)^[5] and possibly EUV lithography (EUVL)^[9] for manufacturing the next generation of semiconductor chips. The beam current in a MIRRORCLE type machine is several amperes, while the beam current in a LINAC is relatively low I_B = 1-100 μA. Thus the development of MIRRORCLE-type sources emitting larger TR power is of significant practical interest for lithography. More recently, storage rings have been used for emission of TR. Storage rings operate at lower electron energies, E_el several tens of MeV, and their electrons pass many times along quasicircular orbits, which results in a much larger I_B. Although we are not aware of any experimental data regarding TR power emitted from storage rings, it has been concluded that the expected emitted TR power from MIRRORCLE should be about 100 mW^[6]. In addition, MIRRORCLE-type sources have irradiation area in the order of 1 inch², allowing the the lithography beam line to be simplified.


The above picture is an example of MIRRORCLE-20SX in a lithography installation.


Measured dependence of the PMT output current count as a function of the emission angle, with 384 nm Al foil target, and without target (background count). This experiment was performed with MIRORRCLE-6X.^[7]




Spectral dependence of E_s(E) the TR energy emitted, within 1 eV around the photon energy, for one pass of one electron through: C foil; Be foil, in MIRRORCLE-20SX. The E_s(E) is the number of emitted TR photons with energies [- 0.5 eV, + 0.5 eV], for one incidence of one electron multiplied by E.^[7]




Spectral dependence of the emitted TR energy^[8], from one interface between material (Be, C, Ti and Au) and vacuum in MIRRORCLE-20SX.

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The product for EUV source user

MIRRORCLE type:	6 MeV model	20 MeV model
X-ray emission scheme	Transition radiation (e.g. Carbon 35 nm foil target)	Trandition radiation (e.g. Be 240 nm foil target)
X-ray energy range	80 eV to 1 keV	80 eV to 10 keV
Irradiation area	85 mrad Φ	25 mrad Φ
Emitted TR power (mW) Designed Measured at April, 2007	65(Carbon 35nm foil target) 3 (Al 385 nm foil target)	810(Be 240nm foil target) 30 (Al 385nm foil target)
Maximum power input	130 kVA	200 kVA
Total size (WDH)	100 x 150 x 130 cm	300 x 600 x 250 cm
Total weight	1 t	3.75 t
Radiation shield	Option
Control system	Automatic standby and operation. Remote monitoring and diagnosis. Emergency shutdown system.

*1 MIRRORCLE's X-ray power very much depends on the vacuum pressure.
It will be increased after while.

Conveniently printable specifications with all models compared can be found in the Literature & CD section of this web site.

Due to continuous improvement, features, specifications and price are subject to change without notification.

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Reference:

[1] M. L. Ter-Mikaelyan, Nucl. Phys. (1961) 24, 43-61.
[2] G. M. Garibyan, Sov. Phys. JETP. (1961) 12, 237-239.
[3] H. Yamada, Jpn. J. Appl. Phys. (1996) 35, L182-L185.
[4] W. Ehrfeld, and D. Munchmeyer, Nucl. Instrum. Methods, (1991) A303, 523-531.
[5] M. A. Piestrup, J. O. Kephart, H. Park, R. K. Klein, R. H. Pantell, O. J. Ebert, M. J. Moran, B. A. Dahling and B. L. Berman, Phys. Rev. A, (1985) 32, 917-927.
[6] M. A. Piestrup, M. W. Powell, J. T. Cremer, L. W. Lombardo, V. V. Kaplin, A. A. Mihal'chuk, S. R. Uglov, V. N. Zabaev, D. M. Skopik, R. M. Silzer, and G. A. Retzlaff, Proc. SPIE, (1998) 3331, 450-463.
[7] N. Toyosugi, H. Yamada, D. Minkov, M. Morita, T. Yamaguchi and S. Imai, J. Synchrotron Rad. (2007) 14, 212-218.
[8] D. Minkov, H. Yamada, N. Toyosugi, T. Yamaguchi, T. Kadono and M. Morita, J. Synchrotron Rad. (2006) 13, 336-342.
[9] G. Shriever, XUV Technologies and Applications, 326th Heraeus Seminar, Bad Honnef, Germany, 7-9 June 2004.

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