Abstract
Abstract
To strengthen the downscaling potential of top-gate amorphous oxide semiconductor (AOS) thin-film transistors (TFTs), the ultra-thin gate insulator (GI) was comparatively implemented using the atomic-layer-deposited (ALD) AlO
x
and HfO
x
. Both kinds of high-k GIs exhibit good insulating properties even with the physical thickness thinning to 4 nm. Compared to the amorphous indium-gallium-zinc oxide (a-IGZO) TFTs with 4 nm AlO
x
GI, the 4 nm HfO
x
enables a larger GI capacitance, while the HfO
x
-gated TFT suffers higher gate leakage current and poorer subthreshold slope, respectively originating from the inherently small band offset and the highly defective interface between a-IGZO and HfO
x
. Such imperfect a-IGZO/HfO
x
interface further causes noticeable positive bias stress instability. Both ALD AlO
x
and HfO
x
were found to react with the underneath a-IGZO channel to generate the interface defects, such as metal interstitials and oxygen vacancies, while the ALD process of HfO
x
gives rise to a more severe reduction of a-IGZO. Moreover, when such a defective interface is covered by the top gate, it cannot be readily restored using the conventional oxidizing post-treatments and thus desires the reduction-resistant pre-treatments of AOSs.
Funder
National Key Research and Development Program
Shenzhen Municipal Scientific Program
Subject
Electrical and Electronic Engineering,Mechanical Engineering,Mechanics of Materials,General Materials Science,General Chemistry,Bioengineering
Cited by
1 articles.
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