Temperature Gradient ZnO Deposited via ALD for High-Performance Transistor Applications

Che, Bowen; Zeng, Hao; Yang, Jun; Qi, Jie; Ding, Xiaobin; Zhang, Jianhua

doi:10.1109/jeds.2020.3015030

Cited by 7 publications

(4 citation statements)

References 24 publications

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“…The low growth rate per cycle (GPC) of ALD, which is undesirable in the case of relatively thick film preparation, would be beneficial in fabricating miniature transistors at a submicron scale with nanoscale thickness. For this reason, various channel materials such as In 2 O 3 , ZnO, − IZO, , IGO, , IGZO, − IZTO, , and ZnON have been studied as active layers in TFTs using the ALD method. Although a promising high mobility (≥50 cm 2 /(V s)) was obtained through design of in situ composition in a few reports, ,, these ALD-derived oxide channel devices were fabricated on a thermal SiO 2 layer as a gate dielectric.…”

Section: Introductionmentioning

confidence: 99%

Achieving a Low-Voltage, High-Mobility IGZO Transistor through an ALD-Derived Bilayer Channel and a Hafnia-Based Gate Dielectric Stack

Cho

Choi

Seul

et al. 2021

ACS Appl. Mater. Interfaces

103

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Ultrahigh-resolution displays for augmented reality (AR) and virtual reality (VR) applications require a novel architecture and process. Atomic-layer deposition (ALD) enables the facile fabrication of indium–gallium zinc oxide (IGZO) thin-film transistors (TFTs) on a substrate with a nonplanar surface due to its excellent step coverage and accurate thickness control. Here, we report all-ALD-derived TFTs using IGZO and HfO2 as the channel layer and gate insulator, respectively. A bilayer IGZO channel structure consisting of a 10 nm base layer (In0.52Ga0.29Zn0.19O) with good stability and a 3 nm boost layer (In0.82Ga0.08Zn0.10O) with extremely high mobility was designed based on a cation combinatorial study of the ALD-derived IGZO system. Reducing the thickness of the HfO2 dielectric film by the ALD process offers high areal capacitance in field-effect transistors, which allows low-voltage drivability and enhanced carrier transport. The intrinsic inferior stability of the HfO2 gate insulator was effectively mitigated by the insertion of an ALD-derived 4 nm Al2O3 interfacial layer between HfO2 and the IGZO film. The optimized bilayer IGZO TFTs with HfO2-based gate insulators exhibited excellent performances with a high field-effect mobility of 74.0 ± 0.91 cm2/(V s), a low subthreshold swing of 0.13 ± 0.01 V/dec, a threshold voltage of 0.20 ± 0.24 V, and an I ON/OFF of ∼3.2 × 108 in a low-operation-voltage (≤2 V) range. This promising result was due to the synergic effects of a bilayer IGZO channel and HfO2-based gate insulator with a high permittivity, which were mainly attributed to the effective carrier confinement in the boost layer with high mobility, low free carrier density of the base layer with a low V O concentration, and HfO2-induced high effective capacitance.

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Section: Introductionmentioning

confidence: 99%

Achieving a Low-Voltage, High-Mobility IGZO Transistor through an ALD-Derived Bilayer Channel and a Hafnia-Based Gate Dielectric Stack

Cho

Choi

Seul

et al. 2021

ACS Appl. Mater. Interfaces

103

View full text Add to dashboard Cite

show abstract

“…This can be attributed to the low surface energy of (002) plane, which is the most thermodynamically favorable 40 , 42 , 43 . When the deposition temperature of film is high, Zn and O atoms can obtain sufficient energy to transfer themselves into energetically favorable positions, which results in ZnO thin films transiting to the (002) preferred orientation at high deposition temperature 44 – 46 . Figure 2d shows the average crystallite sizes of the three different ZnO thin films, which were calculated using Scherrer’s formula.…”

Section: Resultsmentioning

confidence: 99%

CMOS backend-of-line compatible memory array and logic circuitries enabled by high performance atomic layer deposited ZnO thin-film transistor

Wang,

Li,

Lan

et al. 2023

Nat Commun

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The development of high-performance oxide-based transistors is critical to enable very large-scale integration (VLSI) of monolithic 3-D integrated circuit (IC) in complementary metal oxide semiconductor (CMOS) backend-of-line (BEOL). Atomic layer deposition (ALD) deposited ZnO is an attractive candidate due to its excellent electrical properties, low processing temperature below copper interconnect thermal budget, and conformal sidewall deposition for novel 3D architecture. An optimized ALD deposited ZnO thin-film transistor achieving a record field-effect and intrinsic mobility (µFE /µo) of 85/140 cm2/V·s is presented here. The ZnO TFT was integrated with HfO2 RRAM in a 1 kbit (32 × 32) 1T1R array, demonstrating functionalities in RRAM switching. In order to co-design for future technology requiring high performance BEOL circuitries implementation, a spice-compatible model of the ZnO TFTs was developed. We then present designs of various ZnO TFT-based inverters, and 5-stage ring oscillators through simulations and experiments with working frequency exceeding 10’s of MHz.

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“…Growth temperature also influenced the metal-oxygen ratio and impurity levels. A vertical temperature-gradient ZnO-TFT was fabricated and evaluated by Che et al [50]. At 100 • C, lower carrier concentrations and Hall mobility were revealed, compared to a ZnO film fabricated at 200 • C. These authors deposited ZnO front-channels at 200 • C and end on back-channels at 100 • C, and the resulting TFT exhibited enhanced mobility and stability.…”

Section: Importance Of Precursor Chemical Reaction In Amentioning

confidence: 99%

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors: review and outlook

Kim

Kim²,

Kim³

et al. 2023

Int. J. Extrem. Manuf.

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Since the report of amorphous In-Ga-Zn-O (a-IGZO) based thin film transistors (TFTs), interest in oxide semiconductors has increased due to their high mobility, low off-current, low process temperature, and wide flexibility of compositions and processes. However, oxide semiconductors deposited by conventional processes like physical vapor deposition (PVD) leads a problematic issue to produce high-resolution displays and highly integrated memory devices due to the limited process flexibility and the poor conformality on the structured surface. Thus, a need to replace conventional deposition processes has emerged. Atomic layer deposition (ALD) is an advanced technique which could provide conformal, thickness-controlled, and high-quality thin film deposition. From these backgrounds, recently, studies on ALD based oxide semiconductors have dramatically increased. Even so, the relations of film properties of ALD-oxide semiconductors with the main variables associated with deposition and issues related to applications are still less understood than conventional one. In this review, we introduce ALD-oxide semiconductors by providing: (Ⅰ) a brief history and importance of ALD-based oxide semiconductors in the industry, (Ⅱ) a discussion of the value of ALD in oxide semiconductors (in-situ composition control in vertical distribution /vertical structure engineering / chemical reaction and film properties / insulator and interface engineering), and (Ⅲ) an explanation of the challenging issues of scaling oxide semiconductors and ALD in industrial applications. This review provides a valuable perspective for researchers who have interest in semiconductor material and electronic devices by suggesting the reasons why ALD is important in the application of oxide semiconductors.

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Temperature Gradient ZnO Deposited via ALD for High-Performance Transistor Applications

Cited by 7 publications

References 24 publications

Achieving a Low-Voltage, High-Mobility IGZO Transistor through an ALD-Derived Bilayer Channel and a Hafnia-Based Gate Dielectric Stack

Achieving a Low-Voltage, High-Mobility IGZO Transistor through an ALD-Derived Bilayer Channel and a Hafnia-Based Gate Dielectric Stack

CMOS backend-of-line compatible memory array and logic circuitries enabled by high performance atomic layer deposited ZnO thin-film transistor

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors: review and outlook

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