(Invited) Electrical Characterization of Defects in Al2O3

Nanocrystalline high-k dielectrics play a major role in semiconductor research and development. The semiconductor industry faces nanocrystalline dielectrics for MIM capacitors in DRAM devices [1] and rf applications, as well as for gate dielectrics in sub 45 nm devices.

However, the use of crystalline dielectrics lead to new effects like trapping, stress induced leakage currents [2, 3], change in the field extrapolation model of lifetime [4] and an increase of dielectric absorption effects [5]. Most of the described effects are connected to the formation of defect states within the bandgap of the dielectric material. We will review our work on electrical characterization of amorphous and crystalline dielectrics of materials like Al₂O₃, HfO₂, ZrO₂ and SrZrO. The time constants of the dielectric absorption of the dielectrics differ very strongly and mainly for the crystalline dielectrics they show strong load voltage dependence. This can be attributed to a very effective tunneling process into a defect band in the high-k-Material at voltages of 0.6-0.7 V. Additionally, optical stimulated leakage current measurements at 15 K will be shown. Here, defects states in the dielectric and at the interface dielectric-semiconductor can be optically stimulated with IR-light for different sub-band-gap energies.

By the different described methods a detailed characterization of the energy of the investigated bulk and interface traps of the high-K material in combination with Si and GaN substrates are carried out.

[1] J. Heitmann, A. Avellan, T. Boescke, E. Erben, B. Hintze, S. Jakschik, S. Kudelka, and U. Schroeder, ECS. Trans. 2, 217 (2006).

[2] D. Zhou, U. Schroeder, J. Xu, J. Heitmann, G. Jegert, W. Weinreich, M. Kerber, S. Knebel, E. Erben, and T. Mikolajick, J. of Appl. Phys. 108 (2010) 124104.

[3] A. Paskaleva, M. Lemberger, A.J. Bauer, W. Weinreich, J. Heitmann, E. Erben, U. Schröder, and L. Oberbeck,  J. Appl. Phys. 106 (2009) 054107.

[4] R. Agaiby, P. Hofmann, D. Zhou, M. Kerber, J. Heitmann, U. Schroeder, E. Erben, L. Oberbeck, IEEE Elect. Dev. Lett. 30 (4) (2009) 340-342.

[5] M. Kerber, C. Fachmann, J. Heitmann, S. Kudelka, U. Schröder, H. Reisinger, J. Vac. Sci. Technol. B 27(1) (2009) 321-324.