Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016)
    Thin Films Tuesday Sessions
       Session TF-TuP

Paper TF-TuP18
Annealing Behaviors for High-k ZrO2 Grown on Ge

Tuesday, December 13, 2016, 4:00 pm, Room Mauka

Session: Thin Films Poster Session
Presenter: Deuk-Young Kim, Dongguk University, Republic of Korea
Authors: D.-Y. Kim, Dongguk University, Republic of Korea
W.-C. Yang, Dongguk University, Republic of Korea
K.-B. Chung, Dongguk University, Republic of Korea
S. Lee, Dongguk University, Republic of Korea
M.-D. Kim, Chungnam National University, Republic of Korea
H. Lee, Dongguk University, Republic of Korea
N. An, Dongguk University, Republic of Korea
Y. Lee, Dongguk University, Republic of Korea
Correspondent: Click to Email
The thermal annealing behaviors of electrostatic properties for high-k ZrO2 layers were investigated. ZrO2 layers were grown on p-type Ge substrates at 500°C by RF magnetron sputtering. To reduce the native defect density in ZrO2, we adopted the higher oxygen-partial pressure (i.e., O2/Ar > 1). The RF power was 150 W, and the growth time was 20 min. After the growth of ZrO2, the samples were annealed at 600-700°C in Ar ambient by using a rapid thermal annealing method. For the capacitance-voltage characteristics, the as-grown sample exhibited its maximum electrostatic capacitance (i.e., Cmax at the accumulation mode) to drastically decrease with increasing the frequency of ac signals. However, the dielectric characteristics of ZrO2 were much improved after thermal annealing at temperatures above 600°C. Particularly, the magnitude of Cmax was increased by more than 3-times after annealing at 600°C. In addition, Cmax was much stabilized at wide frequency ranges. For higher annealing temperatures, the above feature became more significant. This indicates that the defects in ZrO2 could be effectively eliminated by thermal annealing; particularly, at temperatures above 600°C. Through x-ray photoelectron spectroscopy measurements, we confirmed the above thermal-annealing behaviors to arise from the stabilization of Zr-O bonds due to the interdiffusion of Ge at the interface between ZrO2 and Ge. The best electrostatic permittivity was more than 20, and the equivalent-oxide-thickness was less than 4 nm. Owing to the improvement of interface bonding structures at ZrO2/Ge, the dielectric breakdown field was increased up to ~1 MV/cm. The results suggest that sputter-grown high-k dielectric ZrO2 can be utilized for Ge-based MOS devices, and that thermal annealing is effective to improve the dielectric characteristics of ZrO2.