Determining the ultrafast molecular dynamics of exposed extreme-ultraviolet photoresists

Leuven - PhD
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Meer dan twee weken geleden

Join us to map the ultrafast quantum dynamics of photon-induced ionization processes of photosensitive materials exposed with 13.5 nm (92 eV) extreme ultraviolet photons.

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Join us to map the ultrafast quantum dynamics of photon induced ionization processes of photosensitive materials exposed with 13.5 nm (92 eV) extreme ultraviolet photons. The EUV photolithography process defines semiconductor device circuitry patterns at the sub-7 nanometer technology nodes. This is an exciting opportunity for innovative people to explore ultrafast photon/materials interaction dynamics. In this PhD, the student will use the time-resolved spectroscopies: PhotoEmission Electron Microscopy (PEEM), Ultraviolet Photoemission Spectroscopy (UPS), X-Ray Photoemission Spectroscopy (XPS), EUV, and InfraRed to ascertain the photoionization pathways of photochemically active materials by comparing their spectral results to those generated by computational chemical techniques to assess molecular structure as the ionization process progresses. Along with the spectral work, appropriate materials can be lithographically imaged using interference lithography to produce features as small as 4 nm lines and spaces (8 nm pitch). With this combined information we will seek to improve material imaging performance. (For more description see the last section.)

At imec, we are currently in the process of building AttoLab, a dual beamline high-harmonic source system with time-resolved electron spectroscopy (UPS, XPS, ARPES, PEEMS), IR spectroscopy and coherent diffractive lensless imaging capability on one beamline, and 13.5 nm interference imaging on the other. The spectroscopy lines will use Pump-Probe techniques that work by exciting a sample with a laser, called the pump, and then monitoring the reaction progress with a lower power probe at various times after pump reaction inducement that range from 200 attoseconds to 200 picoseconds delays. These ultrafast monitoring techniques enables us to probe the quantum dynamics of molecules, radicals, ions, clusters, and nanostructures in the condensed phase.

With AttoLab, we do science with anticipation to extend the knowledge gained to practical applications and services. In part we focus on EUV photoresist radiation chemistry in hopes that by understanding the photoionization process we will enable making better photoresists, but the AttoLab goes far beyond that and there will be opportunities to do time-resolved kinetics enabling material development to produce topological insulators, 2D materials, biphotonic and other quantum devices, OLED, biophysical materials, photovoltaics, and batteries.

Imec, in Leuven, Belgium, is a world-class research facility with over four thousand researchers, and, working through KU Leuven, an institution that ranks among the best 50 universities worldwide, we provide doctoral and postdoctoral research opportunities under the guidance of domain experts.

Doctoral candidates must have a master's degree and should desire to be physical photochemists using state-of-the-art high harmonic coherent EUV sources for imaging and kinetics and using time-domain computational chemistry of excited state molecules to aid in interpretation and design of experiments. Candidates must have a background in physical chemistry; and, a working knowledge of high harmonic coherent laser sources is a plus.

More detailed description of these research projects is posted below:

Often in our work we see the initiation of reaction and the result. We don't see the conduit or pathway of energy through the system, nor the chemical kinetics that ensues. Specifically, we do not probe directly the effects of angular momentum which, probably, is a critical aspect of electron-induced chemistry. To this end we're formulating a research that will allow us in the attosecond/femtosecond/picosecond time scale to probe these chemistries with the desire to manipulate them to our benefit and we're looking for a research partners, colleagues and collaborators.

The development of imageable materials for extreme ultraviolet lithography is hindered by a lack of thorough knowledge of their induced-electron chemistry generated by the absorption of the photon. Our premise is that radiation chemistry is driven not just by energy but also by angular momentum and it is both that we need to resolve to study the induced-electron chemistry that occurs during EUV lithographic exposure. Fundamentally we want to understand how an EUV photon is absorbed, the type of subsequent events, their rate and mechanisms of the chemical reactions this absorption causes. This means that during exposure we want to discern ionization (single or multiple), dissociative ionization, ion pair formation, attachment, dissociative attachment of various components in photoresist during EUV exposure. With this knowledge we hope to develop better imaging materials by improving reaction yield, minimizing image blurring and mitigating non-useful reactions and conduits.

To this end we want to record the reaction spectra and to determine conduits to 2 or 3 eV from exposure at 92 eV. The reaction spectra show the reactivity by energy of the secondary electrons that are spawned by photon absorption.  At energies above 30 eV the absorption will be by inner core and below that absorption will be by valence electrons. What we like to know is what molecules absorb, where they absorb (outer core or valence), how well do they absorb (their cross-section), how do they react upon absorption, what is the product of the reaction – a new generation of daughters, an intermediate reactant, a final product that is desired or not, and what are their reaction mechanisms. And, we want to know this across the full range of energies from 92 eV to the lowest reactive energy that is around 2-3 eV. Then with this knowledge we hope to be able to choose reactants that funnels the energy into the end result that we desire with improved efficiency, minimal image blur, and a stochastically meaningful result.

This lack historical knowledge is largely based on the reaction speeds that are too fast to monitor. This has now changed with the advent coherent high harmonic sources where at time scales ranging from atto-/​​femto-seconds on up we can build movies of these induced electron reactions using several complementary techniques. To track absorption and daughter generation we plan, as applicable, to use high speed time resolved variants of:

  1. PEEMS
  2. IR
  3. UPS
  4. XPS
  5. EUV absorption and grazing angle
  6. Other techniques to be determined based on input of domain experts.

 With these techniques, combined with time domain DFT we will know what molecules absorbed and released electrons and then we can track what happens to them upon release. 

Combined with this we plan to use interference imaging of EUV to explore the imaging characteristics to pitches as small as 8 nanometers.


Required background: Physical Chemistry, materials science, and a working knowledge of high harmonic coherent laser sources is a plus

Type of work: 70% experimental, 20% modeling/simulation/10% literature

Supervisor: Stefan De Gendt, ,

Daily advisor: John Petersen

The reference code for this position is 2020-039. Mention this reference code on your application form.

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