| AVS 64th International Symposium & Exhibition | |
| Novel Trends in Synchrotron and FEL-Based Analysis Focus Topic | Wednesday Sessions |
| Session SA+AS+HC+SS-WeA |
| Session: | In Situ and Operando Characterization of Interfacial Reactions in Energy & Electronic Devices |
| Presenter: | Shuichi Ogawa, Tohoku University, Japan |
| Authors: | S. Ogawa, Tohoku University, Japan A. Yoshigoe, JAEA, Japan S. Ishidzuka, National Institute for of Technology, Akita College, Japan Y. Takakuwa, Tohoku University, Japan |
| Correspondent: | Click to Email |
Thermal oxidation of Si surfaces under the non-equilibrium conditions were used to form a high-quality Si oxide films and/or enlarge the oxidation rate. For example, rapid thermal oxidation (RTO) is performed under the raising the temperature, and then thick oxide can be formed without preventing the dopant diffusions[1]. In addition, the oxidation rate of RTO process is faster than that of constant temperature oxidation (CTO) though the highest temperature of RTO is as same as that of CTO[2]. Based on these knowledges, it is predicted that the oxidation rate at the SiO2/Si interface can be quickened even by increase of the O2 pressure. In this study, the increased O2 pressure dependence of the interface oxidation rate which proceeds contentiously after Si(001) surface oxidation was investigated using real-tile photoelectron spectroscopy.
The oxidation experiment was performed using the surface reaction analysis apparatus placed at the BL23SU of SPring-8, Japan. A clean Boron doped p-type Si(001)2×1 surfaces were oxidized at 400℃ under the O2 pressure of 3.2×10-5 Pa. When clean surfaces were completely covered by the Si oxide, the O2 pressure was elevated to PO2(int) in order to enhance the interfacial oxidation. The PO2(int) was changed between 6.4×10-5 Pa to 3.2×10-3 Pa. O 1s and Si 2p spectra were measured repeatedly during the oxidation. The time evolution of O 1s photoelectron intensity (IO1s) was used for investigation of the oxidation rate.
From the IO1s, we can estimate the completion of surface oxidation as 3200 s. An O2 pressure was increased up to 1.5×10-3 Pa at this time, and then the interface oxidation was enhanced. The enhanced interfacial oxidation rates were obtained from the differential of IO1s. The PO2(int) dependence of the interfacial oxidation rate shows that the O2 pressure increase makes the interfacial oxidation rate fast, and the interface oxidation rate is proportional to the square root of PO2(int).
This result cannot be explained using traditional oxidation models, because the proportional relationship between the interface oxidation rate and square root of PO2(int) indicates that the interface oxidation rate is limited by an O2 diffusion through the oxide. However, the thickness oxide is much thinner than 1 nm, so that it cannot be thought that the rate-limiting reaction of interfacial oxidation is O2 diffusion. To explain the kinetics, we propose the new interface oxidation model named “Unified Si oxidation model mediated by point defects”[3].
[1] H.Y.A. Chung, et al., Mater. Sci. Eng. B, 118, 55 (2005).
[2] S. Ogawa et al., J. Chem. Phys., 145, 114701 (2016).
[3] S. Ogawa et al., Jpn. J. Appl. Phys., 46, 7063 (2006).