Paper EM-ThP1
The Effects of VUV Radiation on Low-k Organosilicate Glass (SiCOH) as Measured with Electron-Spin Resonance
Thursday, November 10, 2016, 6:00 pm, Room Hall D
| Session: |
EMPD Poster Session |
| Presenter: |
Panpan Xue, University of Wisconsin-Madison |
| Authors: |
P. Xue, University of Wisconsin-Madison
W. Li, University of Wisconsin-Madison
J. de Marneffe, IMEC, KU Leuven Belgium
M. Baklanov, IMEC, KU Leuven Belgium
V. Afanas'ev, Catholic University of Leuven, Belgium
Y. Nishi, Stanford University
J.L. Shohet, University of Wisconsin-Madison
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| Correspondent: |
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The effects of VUV radiation on defect concentrations in SiCOH are investigated. Electron-spin resonance (ESR) spectroscopy is a very effective tool to detect defects in dielectrics. ESR has been used on various high-k dielectrics, such as HfO2. Here, in order to obtain a clear spectroscopic signal, 60-nm thick SiCOH (k=2.4) was deposited on high-resistivity (3000 Ω-cm) wafers. There are at least two kinds of detectable defects in SiCOH: Si dangling bonds (g=2.0054) and Oxygen vacancies (g=2.0020). In this work, we concentrate on the silicon dangling-bond defects. In order to eliminate dangling bonds from the silicon substrate as well as its edges, CP4 and HF treatments were used. To investigate the influence of VUV radiation, the samples were exposed to synchrotron radiation with a range of photon energies from 7.3 to 21 eV. The ESR measurements showed that the defect concentration of the silicon dangling bonds increased after VUV exposure with photon energies higher than 8eV. In addition, when the photon energy was less than 15 eV, the defect concentration increased with higher photon energy, but did not increase further for VUV exposures with higher photon energies. This is likely caused by electron depletion by photoemission from defects during VUV irradiation. That is, before VUV irradiation, the silicon dangling bonds are filled with electrons. The electrons are then depleted by photoemission during irradiation. Since the band gap for SiCOH is approximately 8 eV,1 this is also consistent with the fact that the energy threshold for Si-H bond photolysis at the surface of H-passivated Si is ~7.9 eV.2 Moreover, VUV exposure can cause a loss of methylated species.3,4 It is possible that the loss of–CH3 groups results in additional Si dangling bonds near the surface of the SiCOH films. The ESR signals have a Lorentzian shape and the Bloch model fits these well. We conclude that silicon dangling bond defects in SiCOH and its interface with silicon can be detected using ESR and that VUV exposure increases the defect concentration.Work supported by the Semiconductor Research Corporation under Contract No. 2012-KJ-2359 and the National Science Foundation under Grant No. CBET-1066231.
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4 J. Lee and D.B. Graves, J. Phys. D: Appl. Phys. 44, 325203 (2011)