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Proceedings Paper

Deep ultraviolet out-of-band contribution in extreme ultraviolet lithography: predictions and experiments
Author(s): Gian F. Lorusso; Natalia Davydova; Mark Eurlings; Cemil Kaya; Yue Peng; Kees Feenstra; Theodore H. Fedynyshyn; Oliver Natt; Peter Huber; Christoph Zaczek; Stuart Young; Paul Graeupner; Eric Hendrickx
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Paper Abstract

Extreme ultraviolet lithography (EUVL) sources emit a broad spectrum of wavelengths ranging from EUV to DUV and beyond. If the deep ultraviolet (DUV) reaches the wafer it will affect imaging performance by exposing the photoresist. Hence it is critical to determine the amount of DUV out of band (OoB) present in a EUVL tool, as well as its effect on the printed features on the wafer. In this study we investigate the effect of DUV OoB in EUVL. A model is developed in order to be able to quantify the DUV/EUV ratio at wafer level and all the required input parameters are estimated in the range from 140 to 400nm, as well as for the EUV at 13.5nm. The transmission of the optical system was estimated based on the optical design and reflectivity measurements of the mirrors. The mask reflectivity for multilayer (ML) and absorber was measured at wavelengths down to 140 nm and for EUV. The sensitivity to EUV and DUV for a variety of resist platforms was measured at 13.5 nm, 157 nm, 193 nm, 248 nm and 365 nm. The source spectra were also measured. By using these inputs, it was possible to estimate the DUV/EUV ratio for two different ASML tool configurations, the EUV Alpha Demo Tool and the NXE:3100. Both NXE:3100 with LPP (laser produced plasma) source and Alpha Demo Tool with DPP (discharge produced plasma) source show less than 1% DUV/EUV ratio in resist. The modeling predictions were compared to experimental results. A methodology is introduced to measure the DUV/EUV ratio at wafer level in situ. With this aim, an aluminum coated mask was fabricated and its reflectivity was qualified in both EUV and DUV wavelength range. By comparing the dose to clear exposures of a reflective blank and of the aluminum mask, it is possible to quantify the DUV/EUV ratio. The experimental results are in order of magnitude agreement with modeling predictions. The proposed experimental approach can be used to benchmark the DUV sensitivity of different resist platforms and may be used to monitor DUV OoB.

Paper Details

Date Published: 8 April 2011
PDF: 8 pages
Proc. SPIE 7969, Extreme Ultraviolet (EUV) Lithography II, 79692O (8 April 2011); doi: 10.1117/12.879381
Show Author Affiliations
Gian F. Lorusso, IMEC (Belgium)
Natalia Davydova, ASML Netherlands B.V. (Netherlands)
Mark Eurlings, ASML Netherlands B.V. (Netherlands)
Cemil Kaya, ASML Netherlands B.V. (Netherlands)
Yue Peng, ASML Netherlands B.V. (Netherlands)
Kees Feenstra, ASML Netherlands B.V. (Netherlands)
Theodore H. Fedynyshyn, MIT Lincoln Lab. (United States)
Oliver Natt, Carl Zeiss SMT AG (Germany)
Peter Huber, Carl Zeiss SMT AG (Germany)
Christoph Zaczek, Carl Zeiss SMT AG (Germany)
Stuart Young, ASML Netherlands B.V. (Netherlands)
Paul Graeupner, Carl Zeiss SMT AG (Germany)
Eric Hendrickx, IMEC (Belgium)


Published in SPIE Proceedings Vol. 7969:
Extreme Ultraviolet (EUV) Lithography II
Bruno M. La Fontaine; Patrick P. Naulleau, Editor(s)

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