EUV spectral purity filter: optical and mechanical design, grating fabrication, and testing

Kierey, Holger; Heidemann, Klaus; Kleemann, Bernd H.; Winters, Renate; Egle, Wilhelm J.; Singer, Wolfgang; Melzer, Frank; Wevers, Rutger; Antoni, Martin

doi:10.1117/12.507741

Cited by 13 publications

(9 citation statements)

References 4 publications

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“…A number of methods to mitigate long wavelength radiation in the optical path of a EUV tool have been demonstrated, and can be grouped by resulting effects: spatial separation of EUV and DUV components, 8 reduction of multilayer mirror reflectivity for non-EUV radiation, 9,10 stopping the DUV and infrared (IR) radiation by free-standing filters transparent for the EUV beam. 11,12 The reflection grating described in 8 was designed to direct the in-band radiation in the first diffraction order into the intermediate focus aperture, deflecting the DUV component out of the beam.…”

Section: Introductionmentioning

confidence: 99%

“…11,12 The reflection grating described in 8 was designed to direct the in-band radiation in the first diffraction order into the intermediate focus aperture, deflecting the DUV component out of the beam. It consisted of several segments with expected diffraction efficiency between 59% (57% measured) and 42% at grazing angles from 7 to 20 deg.…”

Section: Introductionmentioning

confidence: 99%

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Free-standing spectral purity filters for extreme ultraviolet lithography

Чхало

Дроздов

Kluenkov

et al. 2012

J. Micro/Nanolith. MEMS MOEMS

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Free-standing multilayer films consisting of Si, Zr, Mo and silicides of both metals have been fabricated and studied as spectral purity filters (SPF) for extreme ultraviolet (EUV) (13.5 nm) lithography tools. Comparative tests of multilayer SPF structures of various compositions have been performed at high power loads. It was found that a Mo∕ZrSi 2 structure with MoSi 2 capping layers is featured with capability to withstand prolonged heating in vacuum (10 −7 mbar) at 900-950°C. A technique of fabrication of large aperture free-standing multilayers was developed, and a pilot sample of the above film structure of 160 mm in diameter, 50 nm thick, with transparency at 13.5 nm above 70% was fabricated as a conceptual prototype of SPFs with large dimensions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Free-standing spectral purity filters for extreme ultraviolet lithography

Чхало

Дроздов

Kluenkov

et al. 2012

J. Micro/Nanolith. MEMS MOEMS

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“…Projection EUV lithography provides a possibility of designing a spectral purity filter which is essentially a multiple blazed diffraction grating operating in reflection in the in-plane ("classical") grazing-incidence mounting [6]. Such a variable-pitch grating patterned on a high thermal-conductivity substrate can efficiently disperse and focus into the -1 st diffraction order the intense converging broadband radiation produced by an EUV collector.…”

Section: Introductionmentioning

confidence: 99%

Off-plane grazing-incidence fan-groove blazed grating to serve as a high-efficiency spectral purity filter for EUV lithography

Goray

2006

SPIE Proceedings

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Reflecting large-blaze-angle diffraction gratings operating in the off-plane grazing configuration can be used to advantage as high-efficiency tools permitting separation and focusing of a 2%-wavelength about 13.5-nm. A cooled multiple grating with fan-groove geometry is used as a model to select the desired spectral range and obtain a recordhigh efficiency and stigmatic image focusing for a high dispersion in adjacent orders. A maximal relative efficiency of 0.96-0.99 and reflectances of 0.71-0.96 can be readily obtained with an off-plane fine-pitch grating intercepting at incidence angles of 70-85° a converging unpolarized light beam from an EUV collector, a figure higher than that of a grating in an in-plane mount. An absolute efficiency of ~0.72, calculated with a PCGrate®-SX™ code using the AFMmeasured groove profile, is reached in the -1st order of a Mo-coated 200-nm-pitch Si test grating in unpolarized light.

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“…While multilayer-coated diffraction gratings designed for operation near normal incidence in the soft-X-ray-EUV range hold the most promise, rigorous numerical modeling of their efficiency still remains fairly time consuming 3 . The most precise approach to an efficiency analysis of gratings with real, e.g., AFM-measured, groove profiles accounting for microroughness is the method of integral equations, which is applicable to systematic calculations in the short-wavelength range [3][4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

Wavelength separation of plus and minus orders of soft-x-ray-EUV multilayer-coated gratings at near-normal incidence

Goray

Seely

2005

SPIE Proceedings

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The validity of approximating the efficiency of a multilayer grating operating at close to normal incidence in the soft-Xray-EUV range with a product of the relative grating efficiency by the reflectance of its multilayer coating has been studied by the rigorous integral method. The widely used approximated approach has until recently been considered accurate enough for analysis of short-wavelength normal-incidence multilayer-coated gratings. Real gratings employed in the soft-X-ray-EUV range are used to demonstrate the inapplicability of this approximation to an analysis of precise positions of efficiency maxima for the external (n > 0) and internal (n < 0) diffraction orders, despite the small ratios of wavelength and groove depth to period. The present authors have performed an analysis of the accuracy inherent in a derived simple expression for spectral separation of the same plus and minus orders with respect to the wavelength, order's number, incident angle, period, and groove depth. The reason for the observed substantial (a few Angstrom or even nm) wavelength separation between the maxima of positive and negative orders is related to oblique, close-tonormal incidence of radiation on a grating operating in the short-wavelength spectral region and different angles of deviation of respective orders. The modeling carried out with the commercial code PCGrate-S(X) v.6.1 permitted not only prediction of the separation between positive and negative orders for a multilayer Mo/Si 4200-gr/mm grating with AFM-measured trapezoidal groove profile, which is designed for operation in the EIS spectrometer on the Solar-B spacecraft, but obtaining a good agreement with synchrotron radiation measurements, including high orders as well. A conclusion is drawn that high-precision calculations of the efficiency of multilayer normal-incidence soft-X-ray-EUV range gratings have in some cases to be performed, although this may require increasing the computation time by several times compared to the commonly used approximate approach.

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EUV spectral purity filter: optical and mechanical design, grating fabrication, and testing

Cited by 13 publications

References 4 publications

Free-standing spectral purity filters for extreme ultraviolet lithography

Free-standing spectral purity filters for extreme ultraviolet lithography

Off-plane grazing-incidence fan-groove blazed grating to serve as a high-efficiency spectral purity filter for EUV lithography

Wavelength separation of plus and minus orders of soft-x-ray-EUV multilayer-coated gratings at near-normal incidence

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