| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | Haseeb Kazi, University of North Texas |
| Authors: | H. Kazi, University of North Texas R. James, University of North Texas S. Gaddam, University of North texas J.A. Kelber, University of North Texas |
| Correspondent: | Click to Email |
X-ray photoelectron spectroscopy (XPS) and FTIR data indicate that organosilicate glass (OSG) films with backbone carbon (-Si-(CH2)x-Si-) exhibit significantly enhanced resistance to carbon loss upon exposure to O2 plasma, atomic oxygen (O(3P)) and vacuum ultraviolet photons (VUV+O2) at 10-4 Torr O2 compared to films with terminal methyl groups (Si-CH3). Two different low-k films with backbone structures (-Si-(CH2)2-Si-) and (-Si-CH2-Si-) were investigated separately. Films incorporating backbone ethyl groups (-Si-(CH2)2-Si-) were deposited from 1,2 bis (triethoxysilyl) ethane (BTESE) precursor by ebeam or plasma cross-linking with achievable dielectric constant (k) ~3.00. XPS spectra for PECVD and ebeam cross-linked films are similar. The effects of (O(3P)) on ebeam cross-linked film indicates negligible carbon loss or Si oxidation, combined with C-O bond formation, under conditions where OSG films with terminal methyl groups exhibit > 80% carbon loss within the surface region of the film. C-O bond formation is never observed for terminal CH3 groups. Further, backbone carbon (-Si-(CH2)2-Si-) films exposed to VUV+O2 exhibit self-limiting, minimal net carbon loss and formation of C-O bonds within the surface region. In separate experiments, low-k films with methylene bridging unit (-Si-CH2-Si-) were investigated which contains a mixture of (-Si-CH2-Si-) and (-Si-CH3) bonding environments in the final deposited film (k=2.55). Data indicate these backbone carbon (-Si-CH2-Si-) films when exposed to O2 plasma exhibit higher carbon removal rate for terminal groups (-Si-CH3) whereas carbon in the linking chain (-Si-CH2-Si-) undergo relatively slower removal rate, with Si-O, C-O bond formation. This indicates that O2 plasma-induced Si-C bond rupture still occurs in the linking unit, but with a low probability of simultaneous rupture of both Si-C bonds required for abstraction of an in-line methylene bridging group. The data thus demonstrate that OSG films containing backbone carbon groups exhibit greatly reduced rates of carbon loss in the presence of O2 plasma, atomic O or VUV+O2 compared to films with terminal carbon groups due to fundamentally different patterns of Si-C bond scission. The results reported here demonstrate the potential for OSG films with backbone carbon to resist O2 plasma damage.
Acknowledgement: This research was supported by Semiconductor Research Corporation under Task ID: 2561.001. Authors acknowledge Dr. Alfred Grill for providing the carbosilane based backbone low-k films and also acknowledge Dr. Geraud Dubois for stimulating discussions.