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The Faculty of Science and The Leiden Institute of Physics (LION) is looking for a:

PhD candidate: HiTaL: High Throughput Anisotropic Lithography

Leiden Institute of Physics, in collaboration with ASML and ProDrive via a TKI grant (Techniek, Kennis en Innovatie)

Background
Lithography is a crucial step in microchip fabrication. In this technique, light is used to transfer a pattern from a photomask to a photosensitive resist on a Si wafer. The state of the art is extreme ultraviolet (EUV) lithography, which makes use of metal oxide resists (MORs). MORs contain inorganic elements with very high EUV absorption cross section. The absorbed photons generate photoelectrons that in turn generate secondary electrons (SEs). These cause dissociation of ligands, creating active sites that can bond together to form a crosslinked condensed polymer. The exposed resist will thus form an insoluble condensed polymer network. In the subsequent development process, only the exposed parts remain on the Si, resulting in a patterned resist.

The challenge
In EUV lithography, a low photon dose is preferred. But there is a trade-off: photon-shot-noise, blur and defectivity can limit the lithographic definition. A key reason is that the SEs generated are not only active where the photon hits, but are scattered in all directions. Hence, one needs new ways to confine the SEs to an area as small as possible.
We aim to investigate to what extent we can influence confinement by creating anisotropic electron mobility and hence anisotropic crosslinking in the resist layers.

Your project
We will use low-energy electron microscopy (LEEM) as well as other advanced techniques (AFM, XPS, optical spectroscopy) to systematically address the problem, making use of expertise built up in previous collaborations.[1-3] LEEM allows us to irradiate a resist layer with electrons of a well-defined energy in the range 0-95 eV, i.e. any possible electron energy generated by an EUV photon. Our goal is to measure, understand and control the dynamics of the interaction of the electrons with the resist layers. This knowledge should not only lead to scientific publications, but also to novel alleys on how to improve the efficiency, definition and hence throughput of EUV lithography.

Your skills
We are looking for a motivated and skilled experimental physicist or applied physicist (MSc; f/m) who combines scientific curiosity with a hands-on mentality. A background in condensed matter physics, chemistry and/or electron microscopy is helpful. The position requires you to work in a team, collaborating with ASML and ProDrive. You will be based in Leiden, but will perform additional experiments at the ASML facilities.

What we offer
We offer a collaborative, enthusiastic and scientifically strong environment in a renowned research institute, the Leiden institute of Physics, where the input of each person is valued equally. Furthermore, you will be part of a larger team, working with colleagues at ASML and ProDrive. The work is expected to lead to high-impact publications and international visibility. Note that in the Netherlands, a PhD candidate is considered an employee with all the benefits that come with that. Finally, Leiden is a beautiful town close to the beach, with a great academic tradition and atmosphere.

Terms and conditions
We offer a full-time 1 year term position for initially one year. After a positive evaluation of the progress of the thesis, personal capabilities and compatibility the appointment will be extended by a further three years. Salary range from € 2.770,- to €3.539,- gross per month (pay scale P in accordance with the Collective Labor Agreement for Dutch Universities).

Leiden University offers an attractive benefits package with additional holiday (8%) and end-of-year bonuses(8.3 %), training and career development and sabbatical leave. Our individual choices model gives you some freedom to assemble your own set of terms and conditions. Candidates from outside the Netherlands may be eligible for a substantial tax break.

For more information, see https://www.universiteitleiden.nl/en/science and https://workingat.leiden.edu/
All our PhD students are embedded in the Leiden University Graduate School of Science. Our graduate school offers several PhD training courses at three levels: professional courses, skills training and personal effectiveness. In addition, advanced courses to deepen scientific knowledge are offered by the research school.

Promoting an inclusive community is central to Leiden University’s values and vision. Leiden University aims to be an inclusive community in which all students and staff members feel valued and respected, and are able to develop to their full potential. Diversity in experiences and perspectives enriches our teaching and strengthens our research. High-quality education and research means inclusive education and research.

Leiden University
The Leiden Institute of Physics (LION) is one of the oldest physics institutes in the Netherlands with more than 180 staff and around 30 senior scientists. LION is part of the Faculty of Science and covers a very broad spectrum of physics research and education. Theory and experiments go hand in hand at LION: from cosmology to mechanics of DNA, from granular matter to quantum nanoscience.
The Faculty of Science is an excellent faculty where staff and students work together in a dynamic international environment. Personal and academic development are our top priority. Our faculty members are committed to expanding their fundamental knowledge by looking beyond the boundaries of their own discipline; the aim is to benefit science, and to contribute to the major societal challenges of the future.

The research carried out at the Faculty of Science is diverse, ranging from Mathematics, Information science, Astronomy, Physics, Chemistry, Bio-pharmaceutical sciences, Biology and Environmental sciences. Eight institutes organize research activities. These institutes offer eight bachelor’s and twelve master’s programs. Our faculty has grown immensely in recent years. We are located at the heart of Leiden’s Bio Science Park, one of Europe’s largest science parks, where university and business life come together.

Information and application
Applications for this vacancy can be submitted before June 12, 2024 using the blue button of our online system. Please ensure that you include the following documents quoting the vacancy number:

• CV
• Relevant motivation letter with the names of two references.

For more information, please contact:
Prof. Dr. Sense Jan van der Molen, Leiden University (molen@physics.leidenuniv.nl) or
Dr. Syam Parayil Venugopalan, ASML (syam.venugopalan@asml.com)

References
[1] A. Thete, D. Geelen, S. Wuister, S.J. van der Molen, R.M. TrompLow-energy electron (0-100eV) interaction with resists using LEEM
Proc. SPIE 9422: Extreme Ultraviolet (EUV) Lithography VI, 94220A
[2] A. Thete, D. Geelen, S.J. van der Molen & R.M. TrompCharge catastrophe and dielectric breakdown during exposure of organic thin films to low-energy electron radiationPhysical Review Letters 119 (26): 266803 (2017)
[3] Bespalov I., Zhang Y., Haitjema J., Tromp R.M., Molen S.J. van der, Brouwer A.M., Jobst J. & Castellanos S.,
The key role of very-low-energy-electrons in tin-based molecular resists for extreme ultraviolet nanolithography,
ACS Applied Materials and Interfaces 12(8): 9881-9889 (2020)

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