First-ever measurements of ion energy distributionfunctions in EUV induced plasmaCitation for published version (APA):van de Ven, T. H. M., Reefman, P., Osorio, E. A., Banine, V. Y., & Beckers, J. (2016). First-ever measurementsof ion energy distribution functions in EUV induced plasma. Poster session presented at 28th NNV Symposiumon Plasma Physics and Radiation Technology, March 15-16, 2016, Lunteren, The Netherlands, Lunteren,Netherlands.

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/ Department of Applied Physics

28th NNV-SYMPOSIUM on Plasma Physics and Radiation Technology15 and 16 March 2016, Congress Hotel ‘De Werelt’, Lunteren, The Netherlands

Experimental setupThe setup consist of a EUV source, collector ves-sel and measurement vessel. The EQP can be positioned in multiple configurations.

Spectral effectsThe spectrum produced by the EUV source also contains substantial amounts of lower energy Vacuum UV. A spectral filter, with a pass band of 10-20nm can be used to reduce this out of band radiation.

• IEDFs of different species react similar to change in spectrum• VUV increases the ions density due to larger ionization cross section• Addition of VUV doesn’t change IEDF shape• High spectral power creates a high energy shoulder

Surface interactionsIEDFs has been measured with the EQP in parallel and perpendicular configura-tion. In the perpendicular configuration EUV light hits the EQP sample plate. In the parallel configuration there are no surfaces exposed to EUV.

• H2+ is converted to H3

+ by collisions with background: H2+ + H2 → H + H3

+

• Secondary electrons reduce the Te and Vplasma and thereby the ion energy

IntroductionThe EUV sources for ASML’s next-genlithography tools allow us to investigate EUV induced plasmas, which up to recently, have been exclusively investigated by astronomers.

EUV-induced plasmas are of significant im-protance with respect to the lifetime of com-ponents in EUV lithography tools. An impor-tant parameter is the ion energy distribution function (IEDF).

For the first time ion energy distribution func-tions (IEDFs) have been measured in an EUV induced plasma

FIRST-EVER MEASUREMENTS OF ION ENERGY DISTRIBUTION FUNCTIONS IN EUV INDUCED PLASMA

T.H.M. van de Ven1, P. Reefman1, E.A. Osorio2, V.Y. Banine1,2, J. Beckers11Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands2ASML, De Run 6501, 5504 DR Velhoven, The Netherlands

t.h.m.v.d.ven@tue.nl

References[1] Erik Kieft, A relative calibration of the ISAN grazing incidence VUV spectrometer and calibrated spectra of xenon and tin, Thesis TU/e, March 19, 2004

[2] Based on [1] and Filter Transmission Calibration Certificate, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig und Berlin, 2015

The Helix Nebula: a Gaseous Envelope Expelled By a Dying StarNASA, ESA, C.R. O’Dell (Vanderbilt University), M. Meixner and P. McCullough (STScI)

Energy filter(ESA)

Ion optics

Samplingorifice Mass filter

(QMS)

Detector(SEM)

z

zy

x EQP

EQP

EUV-beam

Collector mirrors

Xe discharge(EUV source)

Cone

Opticalfilter

Reductionplate

Focus

Source Collector Measurementvessel

Parallelconfiguration

Perpendicularconfiguration

0 2 4 6 8 10 12 14 16 18 20

102

103

104

105

Energy (eV )

Ion

flux

(cou

nts/

s/eV

)

(V)UV + EUV 30%(V)UV + EUV 100%EUV 100%

EUV induced plasma

0 5 10 15 20 25101

102

103

104

105

106

107

Energy (eV)

Ion

flux

(cou

nst/s

/eV

)

H+

H+2

H+3

0 5 10 15 20 25101

102

103

104

105

106

107

Energy (eV)

Ion

flux

(cou

nst/s

/eV

)

H+

H+2

H+3

Outlook• Verify numerical (PIC) models made by D. Astakhov (ISAN, Russia)• Quantification of ion fluxes to assess EUVL tool lifetime• Investigate scaling laws to deduce ion dynamics

HH +

-

+

92 eV 76 eV

HH +

--- +

76 eV

Setup used, showing the hardware for EUV creation and the measurement equipment.

The Electrostatic Quadrupole Plasma analyser (EQP) used to measure IEDFs.

• Bulk has low energy (<5 eV)• Energy tail up to 22 eV• H2

+ density much lower than H3+

• Broad distribution• Energy cut-off at 18 eV

IEDF of H+ measured with and without Spectral Purity Filter. The filter reduces the total power with 70%, therefore a measurement is done with a reduction plate of 30%.

13.5 20 30 40 50 60 70 80

10−7

10−6

10−5

10−4

10−3

10−2

10−1

Wavelength (nm)

Inte

nsity

(arb

.un

it)

Without filterWith Spectral Purity Filter

The radiation spectrum without[1] and with[2] filter.

300 μJ / pulse

Perpendicular Parallel

IEDFs of hydrogen ions measured in the parallel configuration. The distance from the EUV beam to the EQP was 2,5 cm.

IEDFs of hydrogen ions measured in the perpendicular configuration.