TEOS reaction rates on SiO{sub 2} at 1000K: Zero-order dependence on hydroxyl coverage and implications for reactions with three-membered siloxane rings
We have determined key kinetic parameters for the reaction of TEOS (tetraethylorthosilicate) on SiO{sub 2}. This was accomplished under conditions (20 to 500 mTorr at 1000 K) that pertain directly to TEOS-based CVD (chemical vapor deposition) processes. TEOS reactions were carried out using deuterated silanols (SiOD) on the initial SiO{sub 2} surface. This allowed FTIR (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, SiOH formation exhibited a zero-order dependence on the total coverage of hydroxyl groups. This suggests that reactions with hydroxyl groups alone can not account for all of the TEOS decomposition reactions at 1000 K. Since the low coverage of two-membered siloxane ((Si-O){sub 2}) rings was consumed during the initial TEOS exposure, siloxane (Si-O-Si) bridges in three-membered siloxane ((Si-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.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 135078
- Report Number(s):
- SAND-95-1049C; CONF-951030-2; ON: DE96002543; TRN: 95:008574
- Resource Relation:
- Conference: 42. National Symposium of the American Vacuum Society (AVS), Minneapolis, MN (United States), 16-20 Oct 1995; Other Information: PBD: 1995
- Country of Publication:
- United States
- Language:
- English
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