| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThM |
| Session: | Interconnects II |
| Presenter: | Panpan Xue, University of Wisconsin-Madison |
| Authors: | P. Xue, University of Wisconsin-Madison H. Zheng, University of Wisconsin-Madison W. Li, University of Wisconsin-Madison J.-F. de Marneffe, IMEC M. Baklanov, IMEC, Belgium V. Afanas'ev, Catholic University of Leuven, Belgium Y. Nishi, Stanford University J.L. Shohet, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
Here, we investigate the effects of VUV radiation on the defect concentrations in SiCOH. Electron-spin resonance (ESR) spectroscopy is a very effective tool to detect defects in dielectrics. It has been used on various high-k dielectrics, such as HfO2[1]. In this work, in order to obtain a clear spectroscopic signal, 60nm 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 vacancy (g=2.002). 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 [2] and HF treatments were used. The samples were treated in three ways before ESR (1) CP4 etch that removes surface and edge damage but leaves the SiCOH on the sample. (2) CP4 followed by an HF etch to remove the SiCOH. (3) same as method (2) except here the SiCOH is covered with wax so the HF only etches bare silicon including its edges. Method 3 passivates dangling bonds on the Si surface so any remaining signal should only from the SiCOH. The measurements showed that the sample with SiCOH remaining (method 3) has roughly 1.6 times the number of Si dangling bonds compared with bare Si. In addition, samples having the same edge areas but smaller surface areas were seen to have fewer defects. This shows that the defects measured with ESR are actually from the SiCOH layer but not the edges of the sample. In order to investigate the influence of VUV radiation, the samples were exposed to synchrotron radiation with photon energies of 12 eV for both 10 and 40 minutes. The ESR measurements showed that the defect concentration increased after 10 minutes of VUV exposure and kept increasing with longer VUV exposure times.This is consistent with the fact that the energy threshold for Si-H bond photolysis at the surface of H-passivated Si is ~7.9 eV[3].The ESR signals have a Lorentzian shape and the Bloch model [4] 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.
[1] H. Ren, S. L. Cheng, Y. Nishi, and J. L. Shohet, Applied Physics Letters, 96 192904 (2010)
[2] ANU Centre for Sustainable Energy Systems (CSES), “HNA (HF:Nitric:Acetic) Etch - Full Procedure (also known as ‘CP4 Etch’)” (2009)
[3] A. Pusel, U. Wetterauer, and P. Hess, Phys. Rev. Lett. 81, 645 (1998)
[4] SC Agarwal, Physical Review B, 7 685 (1973)