| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS+TF-ThM |
| Session: | Plasma Deposition and Plasma Enhanced ALD |
| Presenter: | T. Kitajima, National Defense Academy, Japan |
| Authors: | T. Kitajima, National Defense Academy, Japan T. Nakano, National Defense Academy, Japan T.M. Makabe, Keio University, Japan |
| Correspondent: | Click to Email |
1. Introduction
HfSiON is the most applicable chemistry for the high-k gate dielectrics with proper energy band alignment, large area uniformity, and thermal stability. The direct formation of HfSiO film from the Hf overlayer and underlying SiO2 utilizing the thermal interfacial reaction was previously proposed [1]. The process enables remarkably low leak current of the film due to the lack of carbon impurity. We applied N2 plasma for the interfacial reaction and nitridation and realized plasma-based nanoparticle involved non-thermal chemistry for HfSiON.
2. Experiment
The system consists of a UHV-SPM chamber with an e-beam metal evaporation source, a separate VHF (50MHz) low pressure ICP plasma source [2], and ex-situ XPS. Commercial Si(100) wafer with native oxide is introduced to the chamber and Hf and Ti metal beam is exposed to the surface at room temperature. The morphological development of the surface is analyzed with the in-situ non-contact AFM. The N2 ICP is exposed to the sample without any temperature control. The grown film surface is again evaluated on its surface flatness with nc-AFM. The change of the chemistry of the sample surface is analyzed with the XPS.
3. Results and discussion
The AFM image of self-assembled Hf nanoparticles on SiO2 surface after the deposition reveals dome shaped particles with 3-6 nm width are close-packed on the surface with high density of 8.5×1012 cm-2. The N2 ICP exposure induces the interfacial reaction of the Hf nanoparticle/SiO2/Si structure and forms Hf(Ti)SiON(film)/SiON/Si. The angle-resolved Si2p XPS spectrum at 101.5 eV in 30deg. shows the Si included in the film is nitrided. Hf silicate formation is found in the component around 100 eV. The total amount of nitrogen atoms in the film well corresponds to the total supply from the N2 ICP due to the absorption spectroscopy of N(4S) and N(2D) [2].
The AFM image shows the film has superior flatness of RMS roughness of 0.3 nm except the dips of 0.8 nm depth which disappear with Ti addition to the film.
5. Conclusions
The novel film growth process with plasma induced reaction of metal nanoparticles and the substrate is demonstrated for Hf(Ti)SiON. The process scheme is widely applicable to the nano-scale feature modification and chemistry with non-thermal reactions of non-equilibrium plasma.
References
[1] H. Watanabe, M. Saitoh, N. Ikarashi, and T. Tatsumi, Appl. Phys. Lett. 85, 449 (2004).
[2] T. Kitajima, T. Nakano, S. Samukawa, and T. Makabe, Plasma Sources Sci. Technol., 17(2), 024018 (2008).