Soft X-ray absorption and fragmentation of tin-oxo cage photoresists
(2024) In Physical Chemistry Chemical Physics 26(7). p.5986-5998- Abstract
“Tin-oxo cage” organometallic compounds are considered as photoresists for extreme ultraviolet (EUV) photolithography. To gain insight into their electronic structure and reactivity to ionizing radiation, we trapped bare gas-phase n-butyltin-oxo cage dications [(BuSn)12O14(OH)6]2+ in an ion trap and investigated their fragmentation upon soft X-ray photoabsorption by means of mass spectrometry. In complementary experiments, the tin-oxo cages with hydroxide and trifluoroacetate counter-anions were cast in thin films and studied using X-ray transmission spectroscopy. Quantum-chemical calculations were used to interpret the observed spectra. At the carbon K-edge, a distinct pre-edge absorption... (More)
“Tin-oxo cage” organometallic compounds are considered as photoresists for extreme ultraviolet (EUV) photolithography. To gain insight into their electronic structure and reactivity to ionizing radiation, we trapped bare gas-phase n-butyltin-oxo cage dications [(BuSn)12O14(OH)6]2+ in an ion trap and investigated their fragmentation upon soft X-ray photoabsorption by means of mass spectrometry. In complementary experiments, the tin-oxo cages with hydroxide and trifluoroacetate counter-anions were cast in thin films and studied using X-ray transmission spectroscopy. Quantum-chemical calculations were used to interpret the observed spectra. At the carbon K-edge, a distinct pre-edge absorption band can be attributed to transitions in which electrons are promoted from C1s orbitals to the lowest unoccupied molecular orbitals, which are delocalized orbitals with strong antibonding (Sn-C ?*) character. At higher energies, the most prominent resonant transitions involve C-C and C-H ?* valence states and Rydberg (3s and 3p) states. In the solid state, the onset of continuum ionization is shifted by ?5 eV to lower energy with respect to the gas phase, due to the electrostatic effect of the counterions. The O K-edge also shows a pre-edge absorption, but it is devoid of any specific features, because there are many transitions from the different O1s orbitals to a large number of vacant orbitals. In the gas phase, formation of the parent [(BuSn)12O14(OH)6]3+ radical ion is not observed at the C K-edge nor at the O K-edge, because the loss of a butyl group from this species is very efficient. We do observe a number of triply charged photofragment ions, some of which have lost up to 5 butyl groups. Structures of these species are proposed based on quantum-chemical calculations, and pathways of formation are discussed. Our results provide insight into the electronic structure of alkyltin-oxo cages, which is a prerequisite for understanding their response to EUV photons and their performance as EUV photoresists.
(Less)
- author
- organization
- publishing date
- 2024-01
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physical Chemistry Chemical Physics
- volume
- 26
- issue
- 7
- pages
- 13 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- pmid:38293812
- scopus:85183972243
- ISSN
- 1463-9076
- DOI
- 10.1039/d3cp05428d
- language
- English
- LU publication?
- yes
- id
- 6c687912-3a7e-48da-a997-37e0268cddc2
- date added to LUP
- 2024-02-26 13:39:47
- date last changed
- 2024-04-25 21:47:00
@article{6c687912-3a7e-48da-a997-37e0268cddc2,
abstract = {{<p>“Tin-oxo cage” organometallic compounds are considered as photoresists for extreme ultraviolet (EUV) photolithography. To gain insight into their electronic structure and reactivity to ionizing radiation, we trapped bare gas-phase n-butyltin-oxo cage dications [(BuSn)<sub>12</sub>O<sub>14</sub>(OH)<sub>6</sub>]<sup>2+</sup> in an ion trap and investigated their fragmentation upon soft X-ray photoabsorption by means of mass spectrometry. In complementary experiments, the tin-oxo cages with hydroxide and trifluoroacetate counter-anions were cast in thin films and studied using X-ray transmission spectroscopy. Quantum-chemical calculations were used to interpret the observed spectra. At the carbon K-edge, a distinct pre-edge absorption band can be attributed to transitions in which electrons are promoted from C1s orbitals to the lowest unoccupied molecular orbitals, which are delocalized orbitals with strong antibonding (Sn-C ?*) character. At higher energies, the most prominent resonant transitions involve C-C and C-H ?* valence states and Rydberg (3s and 3p) states. In the solid state, the onset of continuum ionization is shifted by ?5 eV to lower energy with respect to the gas phase, due to the electrostatic effect of the counterions. The O K-edge also shows a pre-edge absorption, but it is devoid of any specific features, because there are many transitions from the different O1s orbitals to a large number of vacant orbitals. In the gas phase, formation of the parent [(BuSn)<sub>12</sub>O<sub>14</sub>(OH)<sub>6</sub>]<sup>3+</sup> radical ion is not observed at the C K-edge nor at the O K-edge, because the loss of a butyl group from this species is very efficient. We do observe a number of triply charged photofragment ions, some of which have lost up to 5 butyl groups. Structures of these species are proposed based on quantum-chemical calculations, and pathways of formation are discussed. Our results provide insight into the electronic structure of alkyltin-oxo cages, which is a prerequisite for understanding their response to EUV photons and their performance as EUV photoresists.</p>}},
author = {{Haitjema, Jarich and Castellanos, Sonia and Lugier, Olivier and Bespalov, Ivan and Lindblad, Rebecka and Timm, Martin and Bülow, Christine and Zamudio-Bayer, Vicente and Lau, J. Tobias and von Issendorff, Bernd and Hoekstra, Ronnie and Witte, Katharina and Watts, Benjamin and Schlathölter, Thomas and Brouwer, Albert M.}},
issn = {{1463-9076}},
language = {{eng}},
number = {{7}},
pages = {{5986--5998}},
publisher = {{Royal Society of Chemistry}},
series = {{Physical Chemistry Chemical Physics}},
title = {{Soft X-ray absorption and fragmentation of tin-oxo cage photoresists}},
url = {{http://dx.doi.org/10.1039/d3cp05428d}},
doi = {{10.1039/d3cp05428d}},
volume = {{26}},
year = {{2024}},
}