Studies on Dielectric Properties of Annealed RF-Sputtered ZrO2 Thin Films

Dielectrics play an important role in semiconductor devices when it is used as gate insulator MOS transistors or in memory applications [1]. SiO2 has been one of the most typically used dielectrics due to its good properties like electrical and thermodynamic stability. It provides a great Si-SiO2 interface used in MOS transistors, and has high quality isolation electrical characteristic. Despite its benefits, there comes a point where continuous device scaling sets a limit to what materials can be used. Therefore, other high-k gate dielectric materials have to be found in order to go below 1.5nm thickness when SiO2 is used for the 45nm node technology. ZrO2 is one of the high-k materials that can be used as a possible solution [2].

ZrO2 possesses some interesting characteristics like relatively high-k and wide bandgap. In addition, its crystal structure changes at different temperatures, going from monoclinic to tetragonal and then to cubic as the temperature raises. Even though the monoclinic structure is stable and occurs at room temperature, the other two are not. This presents some problems, which create phase instability leading to stresses and cracking of the material. However, by introducing certain rare earth oxide based dopants as for example Yttria (Y2O3), stable phases for the tetragonal and cubic structures can be achieved, as well as increasing the permittivity constant of the dielectric [3,4].

In this work, ZrO2 thin films are deposited on glass substrates to find various properties. The films are prepared in an RF magnetron sputtering system using a 99.5% pure yttria-stabilized zirconium oxide target. ZrO2 based metal/insulator/metal (MIM) structures are fabricated using Aluminum as the top and bottom electrodes. Various electrical properties are investigated for the ZrO2 films prepared under different deposition and annealing conditions.

REFERENCES

[1] G. D. Wilk, R. M. Wallace, J. M. Anthony, “High-κ gate dielectrics: Current status and materials properties considerations” Journal of Applied Physics, Vol 89, 2001

[2] M. K. Bera, C. K. Maiti, "Reliability of Ultra-thin Zirconium Dioxide (ZrO2) Films on Strained-Si" Physical and Failure Analysis of Integrated Circuits, 2006.

[3] S. M. Hwang, S. M. Lee, K. Park, M. S. Lee, J. Joo, J. H. Lim, H. Kim, J. J. Yoon, Y. D. Kim “Effect of annealing temperature on microstructural evolution and electrical properties of sol-gel processed ZrO2 /Si films” Applied Physics Letters 98, 2011

[4] H. García, H. Castán, S. Dueñas, E. Pérez, L. Bailón, “Electrical characterization of MIS capacitors based on DY203-doped Zr02 dielectrics”, Electron Devices (CDE), 2015