Measuring the electron density in an Extreme Ultra-Violet
generated plasma
Citation for published version (APA):
Horst, van der, R. M., Nijdam, S., & Kroesen, G. M. W. (2013). Measuring the electron density in an Extreme Ultra-Violet generated plasma. 1-1. Poster session presented at 25th NNV Symposium on Plasma Physics and Radiation Technology, March 5-6, 2013, Lunteren, The Netherlands, Lunteren, Netherlands.
Document status and date: Published: 01/01/2013
Document Version:
Accepted manuscript including changes made at the peer-review stage
Please check the document version of this publication:
• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.
• The final author version and the galley proof are versions of the publication after peer review.
• The final published version features the final layout of the paper including the volume, issue and page numbers.
Link to publication
General rights
Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain
• You may freely distribute the URL identifying the publication in the public portal.
If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement:
www.tue.nl/taverne
Take down policy
If you believe that this document breaches copyright please contact us at:
openaccess@tue.nl
providing details and we will investigate your claim.
Measuring the electron density in
an Extreme Ultra-Violet generated
plasma
25th NNV-symposium on Plasma Physics and Radiation Technology.
Lunteren, The Netherlands on March 5-6, 2013.
/ Department of Applied Physics, EPG
R.M. van der Horst, S. Nijdam and G.M.W. Kroesen
Elementary Processes in Gas discharges
r.m.v.d.horst@tue.nl
Introduction
Industries are continuously striving to reduce the size of computer chips in order to meet the demand of increasing computer speed and memory capacity. One way to miniaturize the chips is by reducing the wavelength used in lithography machines by using Extreme Ultra-Vio-let (EUV, 92 eV) light. Background gas in the lithography machine is partially ionized by the absorption of EUV photons. The study of this small low-density (1015 m-3) pulsed plasma is experimentally
challeng-ing.
Goal
Determine the temporally resolved electron density in an EUV gener-ated plasma.
EUV plasma parameters
•
Short (sub-μs) EUV pulse•
EUV transparent gasses (e.g. H2 and He)•
Pressures < 1Pa•
Low electron density (1015 m-3)•
A DC discharge is used as a simulation plasma to test the diag-nosticsMicrowave cavity resonance spectroscopy
Measurement principle and set-up
Results of DC discharge in DC cavity
•
Accuracy of frequency shift: 100 kHz
Detection limit: ne=1014 m-3•
Shift observed due to plasma
Lower responsePreliminary spectrum EUV cavity
•
Accuracy of frequency shift: <20 kHz
Detection limit: ne<3 . 1013 m-3•
Response time: 15 ns•
Resonance frequencies correspond to theoretical values n m f e f f e = e ′ 8 2 0 2 2 0 π φ ε ∆ frequency cavity r esponce f0 ∆f f’ plasma off plasma on –HV microwave generator detector cavity 10 kΩ 6 MΩ antenna plasma isolation 2.660 2.67 2.68 2.69 2.70 2.71 2.72 2.73 2.74 0.05 0.1 0.15 0.2 0.25 0.3 0.35 frequency (GHz) cavity response (mW) no plasma 50 Pa, 2 kV 50 Pa, 3 kV 50 Pa, 4 kV 100 Pa, 3 kVpressure voltage density 50 Pa 2 kV 1.8∙1015 m-3 50 Pa 3 kV 2.2∙1015 m-3 50 Pa 4 kV 2.3∙1015 m-3 100 Pa 3 kV 5.8∙1015 m-3 antenna cavity EUV beam 3 3.5 4 4.5 5 5.5 6 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 frequency (GHz) power (mW) TM010 TM110 f0 = 3.48 GHz σf = 21 MHz Q = f0/σf = 166 τ = 1/(π σf) = 15 ns
Mode Theory Experiment TM010 3.477 GHz 3.482 GHz TM110 5.54 GHz 5.49 GHz
Microwave scattering
•
Oscillating dipole moment in plasma due to MW [1]•
Scattered power has maximum @ fp•
As a first test: determineimpedance of the test plasma [2]
Dip in reflectivity @ a.fp, a<0
Peak in impedance @ fp•
Neither are observedz, E y, k x, B MW transmitting horn MW receiving horn scattered light plasma frequency scatter ed power fp HV– 2 cm 10 k Ω 6 MΩ network analyzer
Conclusion and Outlook
•
No plasma effects visible in plasma scattering measurements
Improve set-up to suppress non-plasma related effects•
MCRS proved to be able to measure 1014 m-3 in a small plasma
Characterize EUV cavity
Measure electron density in EUV generated plasmaAcknowledgements
The authors would like to thank Lex van Deursen for his help with the impedance measurements.
References
[1] Z. Zhang, IEEE Trans. Plasma. Sci. 39:593-595 (2011)
[2] W.E. Amatucci, D.N. Walker, D.D. Blackwell, Navel Research Lab-oratory, NRL/MR/6750-04-8811 (2004)
