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Applied Science and Convergence Technology 2012; 21(5): 273-278

Published online September 1, 2012

Copyright © The Korean Vacuum Society.

Nano-mechanical Properties of Nanocrystal of HfO₂ Thin Films for Various Oxygen Gas Flows and Annealing Temperatures

Joo Young Kim , Soo In Kim , Kyu Young Lee , Ku Eun Kwon , Min Suk Kim , Seoung Hyun Eum , Hyun Jean Jung , Yong Seok Jo , Seung Ho Park , Chang Woo Lee

Abstract

Over the last decade, the hafnium-based gate dielectric materials have been studied for many application fields. Because these materials had excellent behaviors for suppressing the quantum-mechanical tunneling through the thinner dielectric layer with higher dielectric
constant (high-K) than SiO₂ gate oxides. Although high-K materials compensated the deterioration of electrical properties for decreasing the thickness of dielectric layer in MOSFET structure, their nano-mechanical properties of HfO₂ thin film features were hardly known. Thus, we examined nano-mechanical properties of the Hafnium oxide (HfO2) thin film in order to optimize the gate dielectric layer. The HfO₂ thin films were deposited by rf magnetron sputter using hafnium (99.99%) target according to various oxygen gas flows. After deposition, the HfO₂ thin films were annealed after annealing at 400℃, 600℃ and 800℃ for 20 min in nitrogen ambient. From the results, the current density of HfO₂ thin film for 8 sccm oxygen gas flow became better performance with increasing annealing temperature. The nano-indenter and Weibull distribution were measured by a quantitative calculation of the thin film stress. The HfO₂ thin film after annealing at 400℃ had tensile stress. However, the HfO₂ thin film with increasing the annealing temperature up to 800℃ had changed compressive stress. This could be due to the nanocrystal of the HfO₂ thin film. In particular, the HfO₂ thin film after annealing at 400℃ had lower tensile stress, such as 5.35 GPa for the oxygen gas flow of 4 sccm and 5.54 GPa for the oxygen gas flow of 8 sccm. While the HfO₂ thin film after annealing at 800℃ had increased the stress value, such as 9.09 GPa for the oxygen gas flow of 4 sccm and 8.17 GPa for the oxygen gas flow of 8 sccm. From these results, the temperature dependence of stress state of HfO₂ thin films were understood.

Keywords: 전류밀도,나노인덴터,스트레스,하프늄 산화막,와이블 분포,Current density,Nano-indenter,Stress,HfO₂,Weibull distribution

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