Characteristics of Nickel Oxide Modified Zr-Doped HfO2 High-k Thin Films

Abstract

The high-k thin film can be used to replace SiO2 as the gate dielectric in nano MOS devices to improve the performance and reliability (1,2,3). The HfO2 high-k dielectric suffers from the low crystallization temperature, e.g., <600˚C (4,5). The Zr-doped HfO2 (ZrHfO) dielectric has a higher crystallization temperature and better properties than the undoped HfO2 film based on the same EOT (6-9). The sub 1 nm EOT ZrHfO gate dielectric has been demonstrated (6,10). There are reports that high-k dielectric properties could be improved by dispersing metal particles into the structure (11,12). In this work, the authors investigated changes of material and electrical properties of the ZrHfO gate dielectric by embedding nickel oxide (NiO) into the structure.The ZrHfO/NiO/ZrHfO dielectric stack was sputter deposited on a HF pre-cleaned p-type Si (100) wafer in one-pump down. The bottom and top ZrHfO films were deposited from a Hf/Zr target in Ar/O2 at 5 mTorr for 2 min and 10 min, separately. The NiO film was sputter deposited from a Ni target in Ar/O2 at 5 mTorr for 20s. The PDA was done at 800°C under N2 for 60 sec. The nanocrystalline NiO (nc-NiO) was formed in the dielectric layer, as shown in Figure 1. The gate electrode and backside ohmic contact were formed from the sputter deposited Al. The control sample, i.e., ZrHfO gate dielectric without the embedded NiO, was also prepared for comparison.Figure 2 shows C-V hysteresis curves of the control and nc-NiO embedded samples. All samples show counter-clockwise hysteresis. The control sample has a larger hysteresis than the nc-NO embedded sample has, i.e., 0.2V vs. < 0.02V. The large number of trapped charges in the control sample reflects the incomplete passivation of defects in the PDA step (13,14). The small amount of nc-NiO effectively reduced the oxygen deficiencies or vacancies in the film (13,15). The EOTs of the control and nc-NiO embedded samples are 8 nm and 7.7 nm, respectively. The embedded nc-NiO increase of bulk film’s permittivity due to its dipole moment (16). Similar phenomenon was observed in other nanoparticles embedded high-k stack (11,13).The stress-induced leakage current (SILC) of the capacitor was investigated. The leakage current was measured after stress with a negative gate voltage (-Vg ) for various periods. The leakage current increases with the increase of the stress time, which is attributed to the deterioration of the film (17,18). The nc-NiO embedded sample has a large leakage current than the control sample due to its conductive nature (19).More detailed results on the influence of nc-NiO on the breakdown mechanism using the ramp-relax method will be reported (20).This study was partially sponsored by NSF Grant 0926379. C.-H. Yang thanks Professor Way Kuo of City University of Hong Kong for his advice and support throughout this study. The International Technology Roadmap for Semiconductors. Semiconductor Industry Association, December (2003).C. Hu, Nanotech., 10, 113 (1999).J. J. Lee, X. Wang, W. Bai, N. Lu and D.-L. Kwong, IEEE Trans. Elec. Dev., 50, 2067 (2003).J. Robertson, J. Vac. Sci. Technol. B, 18, 1785 (2000).J. Lu, Y. Kuo, J. Yan and C.-H. Lin, Jpn. J. Appl. Phys., 45, L 901 (2006).Y. Kuo, J. Lu, S. Chatterjee, J. Yan, T. Yuan, H.-C. Kim, W. Luo, J. Peterson and M. Gardner, ECS. Trans., 1, 447 (2006).D. Triyoso, ECS Trans., 3, 463 (2006).Y. Kuo, ECS Trans., 3, 253 (2006).Y. Kuo, ECS Trans., 2, 13 (2006).J. Yan, Y. Kuo, and J. Lu, ECS Solid-State Lett., 10, H199 (2007).R. Ravindran, K. Gangopadhyay, S. Gangopadhyay, N. Mehta, and N. Biswas, Appl. Phys. Lett., 89, 263511 (2006).G. C. Vezzoli, M. F. Chen, and J. Caslavsky, Ceram. Int., 23, 105 (1997).C.-H. Lin and Y. Kuo, J. Electrochem. Soc., 158, G162 (2011).N. Zhan, M. C. Poon, C. W. Kok, K. L. Ng, and H. Wong, J. Electrochem. Soc., 150, F200 (2003).H. Sim, H. Chang, and H. Hwang, Jpn. J. Appl. Phys. Part 1, 42, 1596 (2003).S. C. Chung, S. Krüger, G. Pacchioni, and N. Rösch, J. Chem. Phys., 102, 3695 (1995).S. Chatterjee, Y. Kuo, J. Lu, J.-Y. Tewg, and P. Majhi, Microelec. Rel., 46, 69 (2006).S. Chatterjee, Y. Kuo, J. Lu, Microelec. Eng., 85, 202 (2008).J. Feinleib and D. Adler, Phys. Rev. Lett., 21(14), 1010 (1968).W. Luo, Y. Kuo and W. Kuo, IEEE Trans. Dev. Mat. Rel., 4, 488 (2004). Figure 1