Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Rezvanov, A. A.; Attallah, A. G.; Liedke, M. O.; Butterling, M.; Bogdanova, M. A.; Vishnevskiy, A. S.; Seregin, D. S.; Vorotyntsev, D. A. V.; Palov, A. P.; Hirschmann, E.; Wagner, A.; Naumov, S.; Vorotilov, K. A.; Rakhimova, T. V.; Rakhimov, A. T. R.; Baklanov, M.

Modification of spin-on-deposited porous PMO
(periodic mesoporous organosilica) ultralow-k (ULK) SiCOH
films (k = 2.33) containing both methyl terminal and methylene
bridging groups by vacuum ultraviolet (VUV) emission from Xe
plasma is studied. The temporal evolution of chemical composition,
internal defects, and morphological properties (pore structure
transformation) is studied by using Fourier transform infrared
spectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry,
ellipsometric porosimetry (EP), positron-annihilation lifetime
spectroscopy (PALS), and Doppler broadening positron-annihilation spectroscopy. Application of the different advanced diagnostics
allows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure in
the current investigation can be divided into two phases. During the first short phase, film loses almost all of its surface methyl and
matrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage is
found by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when the
treated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUV
exposure time according to PAS and EP data. The last is the result of the additional film shrinkage caused by atmosphere exposure.
During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all the
time as it is expected from in situ ellipsometry, but it is masked by the air exposure

Keywords: ultralow-k materials; vacuum ultraviolet emission; porosimetry; positron-annihilation spectroscopy; in situ ellipsometry

Involved research facilities

  • P-ELBE

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