Structural relaxation in amorphous oxide semiconductor, a-In-Ga-Zn-O

Journal Article · Sun Apr 01 04:00:00 EDT 2012 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3699372· OSTI ID:22036842

Ide, Keisuke; Hiramatsu, Hidenori; Kamiya, Toshio ^[1]; Nomura, Kenji ^[2]; Hosono, Hideo ^[1]

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1. Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)
2. Frontier Research Center, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

Amorphous In-Ga-Zn-O (a-IGZO) is expected as a backplane transistor material to drive next-generation flat-panel and flexible displays. It has been elucidated that thermal annealing even at low temperatures <200 deg. C reduces deep subgap defects and those at {>=}300 deg. C further improve device characteristics, stability, and uniformity. These temperatures are much lower than the reported crystallization temperature (T{sub X}{approx} 600 deg. C). In this work, we investigate effects of thermal annealing on the structural and optical properties of a-IGZO thin films. We performed classical molecular dynamics simulation (CMD) and optical interference analyses including spectroscopic ellipsometry (SE). CMD reproduced the x-ray diffraction pattern of a-IGZO and exhibited a glass transition. Experimentally, it was found that T{sub X} depends largely on deposition methods and conditions, probably due to different chemical compositions. Sputter-deposited a-IGZO films exhibited onset T{sub X}{approx} 600 deg. C and crystalline volume fraction X{sub C} increased linearly from 600 deg. C. 1.2% of film densification occurred even at 600 deg. C due to crystallization. High-temperature in situ SE measurements did not detect a symptom of a glass transition temperature (T{sub g}) presumably because the T{sub X} is close to T{sub g} similar to the case of amorphous metals.

• OSTI ID: 22036842
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 7 Vol. 111; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANNEALING
CRYSTALLIZATION
ELLIPSOMETRY
ENERGY GAP
GALLIUM COMPOUNDS
GLASS
INDIUM COMPOUNDS
MOLECULAR DYNAMICS METHOD
REFLECTIVITY
SEMICONDUCTOR MATERIALS
THIN FILMS
TRANSITION TEMPERATURE
X-RAY DIFFRACTION
ZINC OXIDES