MA/MSc Internship for EUGLOH program

Keywords: lithography, elementary processes, spectroscopy, surface chemistry, radiation damage

Internship Duration: 30/11/-1 - 30/11/-1

Understanding the chemical reactions induced by electron impact on a molecular film is crucial for a wide range of applications, in particular in chemical nanolithography. In a lithographic process, the film is exposed to energetic radiations for structuration or analysis. During these treatments, the interaction of the primary particle (extreme UV or X-ray, high-energy electrons or ions) generates secondary electrons of low-energy (<20 eV) within the film that have a key role for the induced chemistry.
The thesis objective will be to study and quantify the processes at work in order to contribute to the improvement of two chemical nanolithography techniques.
-The Focused Electron Beam Induced Deposition (FEBID) technique [1] uses organometallic precursors. The current challenge in FEBID optimization is to obtain volatile, but robust, precursors, which undergo a controlled fragmentation under irradiation, releasing volatile fragments and leaving a high-purity deposit on the surface. The thesis objectives will be to obtain quantitative values characterising the fragmentation pathways of the irradiated deposits of potential precursors for FEBID applications, by exploring different electronic impact energies. This approach has already been used in the host team on a new precursor for copper deposits.
-A second class of materials will be studied during the thesis, the crosslinking resists (CLR) used in extreme UV lithography. These lithography resins aim to generate a chemical contrast on a surface in a desired pattern, used for selective exposure of surface to an etching treatment in microelectronics. Specifically, CLRs comprise monomers that will bind together under the action of high energy irradiation, providing to the irradiated areas a protective behaviour for the substrate [3]. For these applications, the control of the induced crosslink requires the characterisation of the chemistry induced in these resins, which we have been able to obtained in the laboratory on a similar class of materials [4], [5].
The PhD will be mainly experimental work, with a device we have developed in the ISMO laboratory, dedicated to the study of electron/molecular film interactions. The electron bombardment is controlled between about 1 eV and 2 keV. The effect of the bombardment is measured by mass spectrometry to follow the fragmentation and desorption induced by the electrons impact. The molecular films are probed by thermal desorption spectroscopy and vibrational electron energy loss spectroscopy. Complementary experimental techniques are accessible with the ISMO's new surface science platform (ultra-high vacuum tunnel), including X-ray photoelectron spectroscopy (XPS). The PhD student will benefit from a scientific environment of excellence at European level, initiated by an ELENA NIT network.

Ultra-high Vacuum, surface spectroscopy, mass spectrometrie, electron irradiation,

[1] I. Utke et al. J. Vac. Sci. Technol. B 2008, doi: 10.1116/1.2955728.
[2] L. Sala,et al. Beilstein J. Nanotechnol., 2018, doi: 10.3762/bjnano.9.8.
[3] C. Popescu et al. , doi: 10.1117/12.2258098.
[4] J. Houplin, Langmuir, 2015, doi: 10.1021/acs.langmuir.5b02109.
[5] J. Houplin et al., Phys. Chem. Chem. Phys., 2013, doi: 10.1039/c3cp43750g.

• Pharmacy, Biology, Physics and Chemistry