| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF+EM+MI-WeM |
| Session: | Thin Film Processes for Electronics and Optics I |
| Presenter: | Toshihide Nabatame, National Institute for Materials Science (NIMS), Japan |
| Authors: | T.N. Nabatame, National Institute for Materials Science (NIMS), Japan M. Inoue, National Institute for Materials Science (NIMS) E. Maeda, Shibaura Institute of Technology, Japan K. Yuge, Shibaura Institute of Technology, Japan M. Hirose, Shibaura Institute of Technology, Japan M. Takahashi, Joining and Welding Research Institute, Osaka University, Japan K. Ito, Joining and Welding Research Institute, Osaka University, Japan N. Ikeda, National Institute for Materials Science (NIMS), Japan T. Ohishi, Shibaura Institute of Technology, Japan A. Ohi, National Institute for Materials Science (NIMS), Japan |
| Correspondent: | Click to Email |
GaN-based power devices with metal-oxide-semiconductor (MOS) structure have been widely investigated for next-generation power devices. To reduce the leakage current, Hf-Si-O has one candidate material among various gate insulators. To fabricate Hf-Si-O film, a HfO2/SiO2 laminate film was generally deposited by ALD. The growth mechanism of SiO2 films was greatly changed by the oxidant gas when Tris(dimethylamino)silane (TDMAS) was as precursor [1]. By using ozone gas, the stable growth rate and high quality SiO2 films could be obtained while no growth using H2O gas. We expect that similar data can be also obtained by using oxygen plasma gas. However, the growth mechanism of the SiO2 film during HfO2/SiO2 laminate film deposition and its characteristics have not been fully understood.
In this study, we systematically investigate growth rate of HfO2/SiO2 laminate film by plasma-enhanced ALD (PE-ALD) using TDMAS and Tetrakis(dimethylamino)hafnium (TDMAH) precursors and oxygen plasma gas, and also examine characteristics of the Hf-Si-O films.
The HfO2/SiO2 laminate films were deposited on SiO2/Si substrates by PE-ALD at 300 °C with TDMAH and TDMAS precursors and oxygen plasma gas. The composition Hf/Si ratio of the HfO2/SiO2 laminate films were varied by changing each number of ALD cycle. The SiO2 film was also deposited on SiO2/Si and HfO2/Si substrates by the same PE-ALD condition. The Hf-Si-O films were formed by post-deposition annealing (PDA) at 700 – 900 °C in a N2 atmosphere. The growth per cycle (GPC) of the HfO2/SiO2 laminate, HfO2, and SiO2 films was estimated by spectroscopic ellipsometry, XPS, and cross-sectional TEM measurements. The structure of Hf-Si-O films was identified by XRD analysis, and electrical characteristics of capacitors with Hf-Si-O films were examined using capacitance – voltage measurement.
The GPC of the HfO2/SiO2 laminate, HfO2, and SiO2 films on SiO2/Si substrates were found to be 0.08, 0.08, and 0.04 nm/cycle, respectively, regardless of Hf/Si composition ratio. Considering to the GPC of the HfO2 (0.08 nm/cycle), the estimated GPC of a SiO2 layer during HfO2/SiO2 laminate film deposition was 0.08 nm/cycle, which was unexpected, but increased by about 2 times compared to that of SiO2 film on SiO2/Si substrate. This suggest that an initial adsorption of TDMAS precursor on the SiO2 and HfO2 films must be different and strongly affects to the GPC. The Hf-Si-O films (Hf/Si=2/1) maintains amorphous structure even after PDA temperature at 900 °C. The Hf-Si-O films (Hf/Si=2/1) exhibited high dielectric constant of around 14 as expected.
Reference
[1] L. Han, and Z. Chen, ECS J. of Solid Sate Sci. and Technol., 2 N228 (2013).