Effect of ALD- and PEALD- Grown Al2O3 Gate Insulators on Electrical and Stability Properties for a-IGZO Thin-Film Transistor
This study investigated the electrical and stability characteristics of Al 2 O 3 as a gate insulator, which was deposited by various atomic layer deposition methods in top-gate staggered amorphous InGaZnO (a-IGZO) thin film transistors. A trimethylaluminum precursor was used as an Al source, and H 2...
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Published in | Electronic materials letters Vol. 17; no. 4; pp. 299 - 306 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Seoul
The Korean Institute of Metals and Materials
01.07.2021
Springer Nature B.V 대한금속·재료학회 |
Subjects | |
Online Access | Get full text |
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Summary: | This study investigated the electrical and stability characteristics of Al
2
O
3
as a gate insulator, which was deposited by various atomic layer deposition methods in top-gate staggered amorphous InGaZnO (a-IGZO) thin film transistors. A trimethylaluminum precursor was used as an Al source, and H
2
O gas (H
2
O device) and O
2
plasma with a long plasma time (O
2
LP device) and a short plasma time (O
2
SP device) were used as oxidants. The initial electrical characteristics, including the hysteresis, on–off current ratio, and subthreshold swing, were superior in the H
2
O device compared to the O
2
LP and O
2
SP devices. In the positive bias stress (PBS) results, the degradation characteristics showed a tendency similar to the transfer properties. However, under the negative bias illumination stress (NBIS), the stability of the H
2
O device was significantly reduced compared to the O
2
LP and O
2
SP devices. In this paper, the mechanism of instability, which has opposite results in terms of the PBS and NBIS for the three devices, was identified using capacitance–voltage, three-terminal charge pumping as electrical analysis techniques and secondary ion mass spectroscopy (SIMS) as a physical analysis technique. It was confirmed that the surface oxidation of a-IGZO deteriorates the interfacial properties, causing the transfer characteristics to degrade. The carbon of the Al
2
O
3
film identified via SIMS analysis acts as a trap layer, causing deterioration in the PBS. Alternatively, in the NBIS, it was observed that the carbon acts as a capture site for photo-excited holes, thereby promoting device stability.
Graphic Abstract |
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ISSN: | 1738-8090 2093-6788 |
DOI: | 10.1007/s13391-021-00282-z |