Tetraethylorthosilicate reaction rates on SiO{sub 2} at 1000 K: Zero-order dependence on hydroxyl coverage and implications for reactions with three-membered siloxane rings
- Chemical Processing Sciences Department, Sandia National Laboratories, Albuquerque, New Mexico 87185-0601 (United States)
We have determined key kinetic parameters for the reaction of tetraethylorthosilicate (TEOS) on SiO{sub 2}. This was accomplished under conditions (20{endash}500 mTorr at 1000 K) that pertain directly to TEOS-based chemical vapor deposition processes. TEOS reactions were carried out using deuterated silanols (SiOD) on the initial SiO{sub 2} surface. This allowed Fourier transform infrared spectroscopy measurements to distinguish the consumption of SiOD by TEOS from the concurrent formation of SiOH which results from TEOS decomposition at 1000 K. While SiOD consumption did exhibit a first-order dependence on SiOD coverage, TEOS decomposition exhibited a zero-order dependence on the total coverage of hydroxyl groups. This suggests that reactions with hydroxyl groups alone cannot account for all of the TEOS decomposition reactions at 1000 K. Since the low coverage of two-membered siloxane [(Si{endash}O){sub 2}] rings was consumed during the initial TEOS exposure, siloxane (Si{endash}O{endash}Si) bridges in three-membered siloxane [(Si{endash}O){sub 3}] rings may be the additional species responsible for the constant rate of TEOS decomposition. However, it is not conclusive that this type of site-specific mechanism controls the chemistry. The data may also be explained with a site-independent mechanism in which intramolecular decomposition of TEOS on the surface provides a common rate-determining step for subsequent consumption of hydroxyls and siloxane bridges on SiO{sub 2}. Regardless of the specific mechanism, our results predict that deposition rates will be insensitive to the relative coverages of siloxane bridges and hydroxyls on SiO{sub 2}. Therefore, a precise knowledge of the coverages of these species on SiO{sub 2} is not essential for modeling thermal TEOS decomposition rates. {copyright} {ital 1996 American Vacuum Society}
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 284653
- Report Number(s):
- CONF-9510385--
- Journal Information:
- Journal of Vacuum Science and Technology, A, Journal Name: Journal of Vacuum Science and Technology, A Journal Issue: 3 Vol. 14; ISSN JVTAD6; ISSN 0734-2101
- Country of Publication:
- United States
- Language:
- English
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