Dr. Tero S. Kulmala Profile

Dr. Tero S. Kulmala

Principal Applications Engineer at NIL Technology Switzerland GmbH

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Publications (8)

Proceedings Article | 19 March 2018 Paper

Single-nanometer accurate 3D nanoimprint lithography with master templates fabricated by NanoFrazor lithography

T. Kulmala, C. Rawlings, M. Spieser, T. Glinsner, A. Schleunitz, F. Bullerjahn, F. Holzner

Proceedings Volume 10584, 1058412 (2018) https://doi.org/10.1117/12.2305905

KEYWORDS: Nanoimprint lithography, Silicon, Polymers, Atomic force microscopy, Lithography, Reactive ion etching, Holograms, Etching, Photoresist processing, Scanning probe lithography

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Proceedings Article | 28 April 2017 Presentation

"Non-destructive" dimensional metrology of EUV resist gratings (Conference Presentation)

R. Joseph Kline, Daniel Sunday, Donald Windover, Tero Kulmala, Yasin Ekinci

Proceedings Volume 10145, 101451W (2017) https://doi.org/10.1117/12.2257690

KEYWORDS: Nondestructive evaluation, Scattering, X-rays, Polymethylmethacrylate, Photoresist materials, Critical dimension metrology, Laser scattering, Systems modeling, Dimensional metrology, Extreme ultraviolet

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New critical dimension metrology methods such as critical dimension small angle X-ray scattering (CDSAXS) are being developed to meet the measurement challenges of next generation devices. Two key requirements for any new CD metrology method are non-destructiveness and the measurement speed. We will report on a study of beam damage and scattering strength of two model photoresist systems, HSQ and PMMA. We also will report on the status and initial results from NIST’s upgraded lab CDSAXS system. 50 nm pitch line gratings were fabricated in HSQ and PMMA films using EUV interference lithography at the Swiss Light Source. The lines were about 30 nm tall and 20-30 nm wide. The 17 keV CDSAXS exposure time was varied from 0.1 s to 60 s to determine the minimum X-ray exposure required to obtain a satisfactory fit. Normal incident measurements separated by a blanket X-ray exposure were repeated to measure the decrease in scattering intensity with X-ray dose. The PMMA scattering signal was found to decrease by about 80 % before stabilizing at around 15 % of the original scattering intensity. The HSQ scattering signal decreased much less and stabilized at about 80 % of the original scattering intensity. We also conducted a series of variable-angle CDSAXS measurements as a function of blanket X-ray exposure to determine how the shape of the photoresist lines changed during X-ray exposure. For PMMA, we found the line width to remain constant and the line height to decrease from 25 nm to 10 nm during the exposure series. The exposures that damaged the samples corresponded to several hours of exposure to the synchrotron beam in a 100 µm spot and were much longer than what was required to characterize the line gratings. Smaller targets result in a larger dose and could potentially damage the resist in the time required to make a CDSAXS measurement. The large differences in beam damage between PMMA and HSQ show that resist damage from CDSAXS will depend on the particular resist chemistries and target size.

Proceedings Article | 18 March 2016 Paper

A bottom-up pattern collapse mitigation strategy for EUV lithography

Tero Kulmala, Michaela Vockenhuber, Yasin Ekinci

Proceedings Volume 9776, 97762N (2016) https://doi.org/10.1117/12.2219735

KEYWORDS: Extreme ultraviolet lithography, Extreme ultraviolet, Optical lithography, Lithography, Photoresist materials, Photoresist developing, High volume manufacturing, Integrated circuits, Semiconducting wafers, Nickel, Electroplating, Photoresist processing, Polymers, Capillaries, Liquids

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SPIE Journal Paper | 24 December 2015

Platinum and palladium oxalates: positive-tone extreme ultraviolet resists

Miriam Sortland, Jodi Hotalen, Ryan Del Re, James Passarelli, Michael Murphy, Tero Kulmala, Yasin Ekinci, Mark Neisser, Daniel Freedman, Robert Brainard

JM3, Vol. 14, Issue 04, 043511, (December 2015) https://doi.org/10.1117/12.10.1117/1.JMM.14.4.043511

KEYWORDS: Palladium, Platinum, Magnesium, Extreme ultraviolet, Solids, Metals, Lithography, Extreme ultraviolet lithography, Carbon monoxide, Carbonates

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SPIE Journal Paper | 7 August 2015

Toward 10 nm half-pitch in extreme ultraviolet lithography: results on resist screening and pattern collapse mitigation techniques

Tero Kulmala, Michaela Vockenhuber, Elizabeth Buitrago, Roberto Fallica, Yasin Ekinci

JM3, Vol. 14, Issue 03, 033507, (August 2015) https://doi.org/10.1117/12.10.1117/1.JMM.14.3.033507

KEYWORDS: Line edge roughness, Extreme ultraviolet lithography, Extreme ultraviolet, Semiconducting wafers, Photomasks, Scanning electron microscopy, Lithography, Diffraction, Diffraction gratings, Optical lithography

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Proceedings Article | 6 April 2015 Paper

Toward 10nm half-pitch in EUV lithography: results on resist screening and pattern collapse mitigation techniques

Tero Kulmala, Michaela Vockenhuber, Elizabeth Buitrago, Roberto Fallica, Yasin Ekinci

Proceedings Volume 9422, 942204 (2015) https://doi.org/10.1117/12.2085936

KEYWORDS: Line edge roughness, Extreme ultraviolet lithography, Extreme ultraviolet, Semiconducting wafers, Scanning electron microscopy, Optical lithography, Chemically amplified resists, Lithography, Photomasks, Liquids

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Proceedings Article | 3 March 2014 Paper

Graphene saturable absorbers for VECSELs

V. Wittwer, C. Zaugg, Z. Sun, D. Popa, S. Milana, T. Kulmala, R. Sundaram, M. Mangold, M. Golling, Y. Lee, J. Ahn, U. Keller, A. Ferrari

Proceedings Volume 8966, 89660X (2014) https://doi.org/10.1117/12.2039111

KEYWORDS: Silica, Graphene, Mirrors, Mode locking, Absorption, Dielectrics, Wavelength tuning, Ultrafast phenomena, Semiconductor lasers, Pulsed laser operation

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Proceedings Article | 3 March 2014 Paper

Graphene modelocked VECSELs

C. Zaugg, V. Wittwer, Z. Sun, D. Popa, S. Milana, T. Kulmala, R. Sundaram, M. Mangold, M. Golling, Y. Lee, J. Ahn, A. Ferrari, U. Keller

Proceedings Volume 8966, 896607 (2014) https://doi.org/10.1117/12.2038336

KEYWORDS: Silica, Mirrors, Absorption, Graphene, Mode locking, Reflectivity, Refractive index, Interfaces, Semiconductor lasers, Semiconductors

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Showing 5 of 8 publications

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