Dr. Markus Foltin Profile

Dr. Markus Foltin

at SUSS MicroTec Solutions GmbH & Co KG

SPIE Involvement:

Author

Publications (3)

SPIE Journal Paper | 21 June 2023

Evaluation of Ta-Co alloys as novel high-k extreme ultraviolet mask absorber

Devesh Thakare, Meiyi Wu, Karl Opsomer, Qais Saadeh, Victor Soltwisch, Philipp Naujok, Christophe Detavernier, Davide Dattilo, Markus Foltin, Andy Goodyear, Mike Cooke, Annelies Delabie, Vicky Philipsen

JM3, Vol. 22, Issue 02, 024403, (June 2023) https://doi.org/10.1117/12.10.1117/1.JMM.22.2.024403

KEYWORDS: Alloys, Extreme ultraviolet, Tantalum, Nanoimprint lithography, Etching, Oxides, Silicon, Ruthenium, Light sources and illumination, Film thickness

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SPIE Journal Paper | 3 May 2021

Study of novel EUVL mask absorber candidates

Meiyi Wu, Devesh Thakare, Jean-François de Marneffe, Patrick Jaenen, Laurent Souriau, Karl Opsomer, Jean-Philippe Soulié, Andreas Erdmann, Hazem M. Mesilhy, Philipp Naujok, Markus Foltin, Victor Soltwisch, Qais Saadeh, Vicky Philipsen

JM3, Vol. 20, Issue 02, 021002, (May 2021) https://doi.org/10.1117/12.10.1117/1.JMM.20.2.021002

KEYWORDS: Photomasks, Extreme ultraviolet lithography, Extreme ultraviolet, Nanoimprint lithography, Etching, Ruthenium, Refractive index, Optical lithography, Semiconducting wafers, Thin films

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Novel mask absorber designs are catching the attention of the EUVL community due to their ability to mitigate mask 3D effects. Material selection is part of such an optimization. We propose several candidates as novel EUV lithography mask absorbers, namely TaTeN, Ru–Ta, and Pt–Mo alloys. The choice of these materials is based on their theoretical performance evaluated by EUV imaging simulation based on their complex refractive index N ( λ ) = n ( λ ) + ik ( λ ) , where the optical constants n and k relate to the phase velocity and the absorption of electromagnetic radiation with a wavelength λ, respectively. The materials are deposited as thin films on Si substrate with an additional Ru layer to mimic the cap of the multilayer mirror on the real mask. The experimental n and k values are determined by analyzing EUV reflectivity data obtained using a 13.5-nm synchrotron EUV radiation. The imaging simulation presented consists of calculating several imaging metrics including non-telecentricity, normalized image log-slope, and threshold-to-size for specific use cases using the novel absorber. It also compares the proposed materials with the reference TaBN absorber. TaTeN shows higher absorption than TaBN and refraction closer to 1, which improves phase matching for a high k absorber. The refractive index of Ru–Ta and Pt–Mo alloys exhibits a large difference from that of air and provides the required phase shift of attenuated phase shift masks. The characterizations of these materials target the requirements of an EUVL mask: durability for mask cleaning, mask lifetime, and etchability for mask patterning. The stability is first tested against several standard mask cleaning solutions by a beaker test for up to 24 h. The samples are also exposed to hydrogen plasma to imitate the working environment in an EUV scanner. Concerning material patterning, chemical reactive ion etch is applied for preliminary tests. A proper etch recipe is found for TaTeN with a good etch rate (about 60 nm / min) and good selectivity to the Ru underlayer (Ru etch is negligible).

Proceedings Article | 20 October 2020 Presentation + Paper

Mask absorber for next generation EUV lithography

Meiyi Wu, Devesh Thakare, Jean-François de Marneffe, Patrick Jaenen, Laurent Souriau, Karl Opsomer, Jean-Philippe Soulié, Andreas Erdmann, Hazem Mesilhy, Philipp Naujok, Markus Foltin, Victor Soltwisch, Qais Saadeh, Vicky Philipsen

Proceedings Volume 11517, 1151706 (2020) https://doi.org/10.1117/12.2572114

KEYWORDS: Photomasks, Extreme ultraviolet lithography, Extreme ultraviolet, Etching, Ruthenium, X-rays, Refractive index, Reflectivity, Phase shifts, Mask cleaning

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Novel mask absorber designs are calling attention of the EUVL community due to their ability to mitigate mask 3D effects. Material selection is part of such optimization [1]. In this paper we propose several candidates as novel EUV lithography mask absorbers, namely TaTeN, Ru-Ta and Pt-Mo alloys. The choice of these materials is based on their theoretical performance evaluated by EUV imaging simulation based on their complex refractive index N(λ) = n(λ) +ik(λ), where the optical constants n and k relate to the phase velocity and to the absorption of an electromagnetic radiation with a wavelength λ, respectively. The materials are deposited as thin films on Si substrate with an additional Ru layer to mimic the cap of multilayer mirror (MLM) on the real mask. The experimental n and k values are determined by analyzing EUV reflectivity data obtained using a 13.5 nm synchrotron EUV radiation. The imaging simulation presented in this paper consists of calculation of several imaging metrics like non-telecentricity, normalized image log-slop (NILS), and threshold-to-size for specific use cases using the novel absorber. It also compares the proposed materials to the reference TaBN absorber. TaTeN shows higher absorption than TaBN and refraction closer to 1, which improves phase matching for a high k absorber. The refractive index of Ru-Ta and Pt-Mo alloys exhibits a large difference to that of air and provides the required phased shift of attenuated phase shift masks [2]. The characterizations of these materials target the requirements of an EUVL mask: durability for mask cleaning, mask lifetime and etchablity for mask patterning. The stability is first tested against several standard mask cleaning solutions by beaker test up to 24 hours with the film structure monitored by X-ray reflectivity analysis. The samples are also exposed to hydrogen plasma to imitate the working environment in a EUV scanner. Material integrity is checked with Rutherford backscattering spectroscopy before and after the exposure. Concerning material patterning, chemical reactive ion etch is applied for preliminary tests. A proper etch recipe is found for TaTeN with good etch rate (about 60 nm/min) and good selectivity to Ru underlayer (Ru etch is ignorable).

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