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양자나노과학 연구단
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Low interface trap density in scaled bilayer gate oxides on 2D materials via nanofog low temperature atomic layer deposition

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Title
Low interface trap density in scaled bilayer gate oxides on 2D materials via nanofog low temperature atomic layer deposition
Author(s)
Iljo Kwak; Mahmut Kavrik; Jun Hong Park; Larry Grissom; Bernd Fruhberger; Keith T. Wong; Sean Kang; Andrew C. Kummel
Publication Date
2019-01
Journal
APPLIED SURFACE SCIENCE, v.463, no.1, pp.758 - 766
Publisher
ELSEVIER SCIENCE BV
Abstract
Al2O3 and Al2O3/HfO2 bilayer gate stacks were directly deposited on the surface of 2D materials via low temperature ALD/CVD of Al2O3 and high temperature ALD of HfO2 without any surface functionalization. The process is self-nucleating even on inert surfaces because a chemical vapor deposition (CVD) component was intentionally produced in the Al2O3 deposition by controlling the purge time between TMA and H2O precursor pulses at 50 °C. The CVD growth component induces formation of sub-1 nm AlOx particles (nanofog) on the surface, providing uniform nucleation centers. The ALD process is consistent with the generation of sub-1 nm gas phase particles which stick to all surfaces and is thus denoted as nanofog ALD. To prove the ALD/CVD Al2O3 nucleation layer has the conformality of a self-limiting process, the nanofog was deposited on a high aspect ratio Si3N4/SiO2/Si pattern surface; conformality of >90% was observed for a sub 2 nm film consistent with a self-limiting process. MoS2 and HOPG (highly oriented pyrolytic graphite) metal oxide semiconductor capacitors (MOSCAPs) were fabricated with single layer Al2O3 ALD at 50 °C and with the bilayer Al2O3/HfO2 stacks having Cmax of ∼1.1 µF/cm2 and 2.2 µF/cm2 respectively. In addition, Pd/Ti/TiN gates were used to increase Cmax by scavenging oxygen from the oxide layer which demonstrated Cmax of ∼2.7 µF/cm2. This is the highest reported Cmax and Cmax/Leakage of any top gated 2D semiconductor MOSCAP or MOSFET. The gate oxide prepared on a MoS2 substrate results in more than an 80% reduction in Dit compared to a Si0.7Ge0.3(0 0 1) substrate. This is attributed to a Van der Waals interaction between the oxide layer and MoS2 surface instead of a covalent bonding allowing gate oxide deposition without the generation of dangling bonds. © 2018
URI
https://pr.ibs.re.kr/handle/8788114/5311
ISSN
0169-4332
Appears in Collections:
Center for Quantum Nanoscience(양자나노과학 연구단) > Journal Papers (저널 논문)
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