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17 pages, 2978 KiB

Open AccessArticle

Atomic Layer Deposition of Ultra-Thin Crystalline Electron Channels for Heterointerface Polarization at Two-Dimensional Metal-Semiconductor Heterojunctions

by Mohammad Karbalaei Akbari, Nasrin Siraj Lopa and Serge Zhuiykov

Coatings 2023, 13(6), 1041; https://doi.org/10.3390/coatings13061041 - 03 Jun 2023

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Abstract

Atomic layer deposition (ALD) has emerged as a promising technology for the development of the next generation of low-power semiconductor electronics. The wafer-scaled growth of two-dimensional (2D) crystalline nanostructures is a fundamental step toward the development of advanced nanofabrication technologies. Ga₂O [...] Read more.

Atomic layer deposition (ALD) has emerged as a promising technology for the development of the next generation of low-power semiconductor electronics. The wafer-scaled growth of two-dimensional (2D) crystalline nanostructures is a fundamental step toward the development of advanced nanofabrication technologies. Ga₂O₃ is an ultra-wide bandgap metal oxide semiconductor for application in electronic devices. The polymorphous Ga₂O₃ with its unique electronic characteristics and doping capabilities is a functional option for heterointerface engineering at metal-semiconductor 2D heterojunctions for application in nanofabrication technology. Plasma-enhanced atomic layer deposition (PE-ALD) enabled the deposition of ultra-thin nanostructures at low-growth temperatures. The present study used the PE-ALD process for the deposition of atomically thin crystalline ß-Ga₂O₃ films for heterointerface engineering at 2D metal-semiconductor heterojunctions. Via the control of plasma gas composition and ALD temperature, the wafer-scaled deposition of ~5.0 nm thick crystalline ß-Ga₂O₃ at Au/Ga₂O₃-TiO₂ heterointerfaces was achieved. Material characterization techniques showed the effects of plasma composition and ALD temperature on the properties and structure of Ga₂O₃ films. The following study on the electronic characteristics of Au/Ga₂O₃-TiO₂ 2D heterojunctions confirmed the tunability of this metal/semiconductor polarized junction, which works as functional electron channel layer developed based on tunable p-n junctions at 2D metal/semiconductor interfaces. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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9 pages, 1902 KiB

Open AccessCommunication

Adsorption and Surface Diffusion of Atomic Ru on TiN and SiO₂: A First-Principles Study

by Changhyun Ahn, Ju Hyeon Jung, Jae Jung Kim, Dong-Chan Lee and Bonggeun Shong

Coatings 2023, 13(6), 1020; https://doi.org/10.3390/coatings13061020 - 31 May 2023

Cited by 2 | Viewed by 1712

Abstract

Ruthenium (Ru) has been suggested as one of the promising materials for nanoscale interconnects to substitute copper (Cu) that is currently used in the semiconductor industry. Through density functional theory (DFT) calculations, we present the rationales for varying deposition behavior of Ru on [...] Read more.

Ruthenium (Ru) has been suggested as one of the promising materials for nanoscale interconnects to substitute copper (Cu) that is currently used in the semiconductor industry. Through density functional theory (DFT) calculations, we present the rationales for varying deposition behavior of Ru on different types of substrates. For the SiO₂ and TiN substrates, with and without adsorbed hydrogen, our calculation results reveal the adsorption sites and their adsorption energy, the surface diffusion paths and their activation energy, and the surface diffusion coefficients. We confirm that the adsorption of Ru is more stable on TiN than on SiO₂ substrates, and that the surface diffusion of Ru adatom is faster on TiN than on SiO₂ surface. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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12 pages, 4983 KiB

Open AccessArticle

Enhanced Stability of Solution-Processed Indium–Zinc–Tin–Oxide Transistors by Tantalum Cation Doping

by Haiyang Xu, Pingping Li, Zihui Chen, Bing Yang, Bin Wei, Chaoying Fu, Xingwei Ding and Jianhua Zhang

Coatings 2023, 13(4), 767; https://doi.org/10.3390/coatings13040767 - 13 Apr 2023

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Abstract

Highly stable metal oxide thin film transistors (TFTs) are required in high-resolution displays and sensors. Here, we adopt a tantalum cation (Ta⁵⁺) doping method to improve the stability of zinc–tin–oxide (ZnSnO) TFTs. The results show that Ta⁵⁺-doped TaZnSnO TFT [...] Read more.

Highly stable metal oxide thin film transistors (TFTs) are required in high-resolution displays and sensors. Here, we adopt a tantalum cation (Ta⁵⁺) doping method to improve the stability of zinc–tin–oxide (ZnSnO) TFTs. The results show that Ta⁵⁺-doped TaZnSnO TFT with 1 mol% concentration exhibits excellent stability. Compared with the undoped device, the oxygen vacancy defects of TaZnSnO thin films reduce from 38.05% to 18.70%, and the threshold voltage shift (ΔV_th) reduces from 2.36 to 0.71 V under positive bias stress. We attribute the improved stability to the effective suppression of the oxygen vacancy defects, which is confirmed by the XPS results. In addition, we also prepared TaInZnSnO TFT devices with 1 mol% Ta⁵⁺ doping concentration. Compared with the 1 mol% Ta⁵⁺-doped TaZnSnO TFTs, the μ increases two-fold from 0.12 to 0.24 cm²/Vs, and the V_th decreases from 2.29 to 0.76 V in 1 mol% Ta⁵⁺-doped TaInZnSnO TFT with an In:Zn:Sn ratio of 4:4:3, while the device remains highly stable with a ΔV_th of only 0.90 V. The injection of Ta⁵⁺ provides a novel strategy for the enhancement of the stability in ZnSnO-based TFTs. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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10 pages, 9261 KiB

Open AccessFeature PaperArticle

Water-Free SbO_x ALD Process for Coating Bi₂Te₃ Particles

by Sebastian Lehmann, Fanny Mitzscherling, Shiyang He, Jun Yang, Martin Hantusch, Kornelius Nielsch and Amin Bahrami

Coatings 2023, 13(3), 641; https://doi.org/10.3390/coatings13030641 - 18 Mar 2023

Cited by 1 | Viewed by 1295

Abstract

We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbO_x using SbCl₅ and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi₂Te₃ particles synthesized via the solvothermal [...] Read more.

We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbO_x using SbCl₅ and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi₂Te₃ particles synthesized via the solvothermal route to enhance the thermoelectric properties (i.e., Seebeck coefficient, thermal and electrical conductivity) via interface engineering. The amorphous character of the coating was shown by the missing reflexes on the X-ray diffractograms (XRD). A shift from the oxidation state +III to +V of the Sb species was observed using X-ray photoelectron spectroscopy (XPS), indicating increased thickness of the SbO_x coating layer. Additionally, a peak shift of the Sb 3d_5/2 + O 1s peak indicated increased n-type doping of the material. Electrical measurements of spark plasma-sintered bulk samples confirmed the doping effect on the basis of decreased specific resistivity with increasing SbO_x layer thickness. The Seebeck coefficient was improved for the coated sample with 500 cycles of SbO_x, while the total thermal conductivity was reduced, resulting in enhancement of the zT. The results distinctly show that surface engineering via powder ALD is an effective tool for improving key properties of thermoelectric materials like electrical conductivity and the Seebeck coefficient. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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10 pages, 3404 KiB

Open AccessCommunication

Al₂O₃ Ultra-Thin Films Deposited by PEALD for Rubidium Optically Pumped Atomic Magnetometers with On-Chip Photodiode

by Florival M. Cunha, Manuel F. Silva, Nuno M. Gomes and José H. Correia

Coatings 2023, 13(3), 638; https://doi.org/10.3390/coatings13030638 - 17 Mar 2023

Cited by 1 | Viewed by 1764

Abstract

This communication shows the recipe for plasma-enhanced atomic layer deposition (PEALD) Al₂O₃ ultra-thin films with thicknesses below 40 nm. Al₂O₃ ultra-thin films were deposited by PEALD to improve the rubidium optically pumped atomic magnetometers’ (OPMs) cell lifetime. [...] Read more.

This communication shows the recipe for plasma-enhanced atomic layer deposition (PEALD) Al₂O₃ ultra-thin films with thicknesses below 40 nm. Al₂O₃ ultra-thin films were deposited by PEALD to improve the rubidium optically pumped atomic magnetometers’ (OPMs) cell lifetime. This requirement is due to the consumption of the alkali metal (rubidium) inside the vapor cells. Moreover, as a silicon wafer was used, an on-chip photodiode was already integrated into the fabrication of the OPM. The ALD parameters were achieved with a GPC close to 1.2 Å/cycle and the ALD window threshold at 250 °C. The PEALD Al₂O₃ ultra-thin films showed a refractive index of 1.55 at 795 nm (tuned to the D1 transition of rubidium for spin-polarization of the atoms). The EDS chemical elemental analysis showed an atomic percentage of 58.65% for oxygen (O) and 41.35% for aluminum (Al), with a mass percentage of 45.69% for O and 54.31% for Al. A sensitive XPS surface elemental composition confirmed the formation of the PEALD Al₂O₃ ultra-thin film with an Al 2s peak at 119.2 eV, Al 2p peak at 74.4 eV, and was oxygen rich. The SEM analysis presented a non-uniformity of around 3%. Finally, the rubidium consumption in the coated OPM was monitored. Therefore, PEALD Al₂O₃ ultra-thin films were deposited while controlling their optical refractive index, crystalline properties, void fraction, surface roughness and thickness uniformity (on OPM volume 1 mm × 1 mm × 0.180 mm cavity etched by RIE), as well as the chemical composition for improving the rubidium OPM lifetime. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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9 pages, 7819 KiB

Open AccessFeature PaperArticle

Effect of Titanium Cation Doping on the Performance of In₂O₃ Thin Film Transistors Grown via Atomic Layer Deposition

by Bing Yang, Pingping Li, Zihui Chen, Haiyang Xu, Chaoying Fu, Xingwei Ding and Jianhua Zhang

Coatings 2023, 13(3), 605; https://doi.org/10.3390/coatings13030605 - 12 Mar 2023

Cited by 2 | Viewed by 1508

Abstract

Indium oxide semiconductors, as one of the channel materials for thin film transistors (TFTs), have been extensively studied. However, the high carrier concentration and excess oxygen defects of intrinsic In₂O₃ can cause the devices to fail to work properly. We [...] Read more.

Indium oxide semiconductors, as one of the channel materials for thin film transistors (TFTs), have been extensively studied. However, the high carrier concentration and excess oxygen defects of intrinsic In₂O₃ can cause the devices to fail to work properly. We overcame this hurdle by incorporating the titanium cation (Ti⁴⁺) into In₂O₃ via atomic layer deposition (ALD). The InTiO_x TFTs with an In:Ti atomic ratio of 15:1 demonstrated excellent electrical and optical properties, such as a lower threshold voltage (V_th) of 0.17 V, a lower subthreshold swing (SS) of 0.13 V/dec., a higher I_on/I_off ratio of 10⁷, and a transmittance greater than 90% in the visible region. With the doping ratio increasing from 20:1 to 10:1, the mobility decreased from 9.38 to 1.26 cm²/Vs. The threshold voltage shift (ΔV_th) of InTiO (15:1) under 5 V positive bias stress (PBS) for 900 s is 0.93 V, which is less than other devices. The improvement in stability with increasing Ti⁴⁺ concentrations is attributed to the reduction of oxygen defects. Therefore, these InTiO (15:1) TFTs with excellent performance show great potential for future applications in transparent electronic devices. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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11 pages, 9747 KiB

Open AccessArticle

The Effect of Deposition Temperature of TiN Thin Film Deposition Using Thermal Atomic Layer Deposition

by Baek-Ju Lee, Yoo-Seong Kim, Dong-Won Seo and Jae-Wook Choi

Coatings 2023, 13(1), 104; https://doi.org/10.3390/coatings13010104 - 05 Jan 2023

Cited by 2 | Viewed by 3615

Abstract

In this study, the effect of deposition temperature of TiN thin films deposited using the thermal atomic layer deposition (ALD) method was investigated. TiCl₄ precursor and NH₃ reactive gas were used, and the deposition rate, resistivity change, and surface morphology characteristics [...] Read more.

In this study, the effect of deposition temperature of TiN thin films deposited using the thermal atomic layer deposition (ALD) method was investigated. TiCl₄ precursor and NH₃ reactive gas were used, and the deposition rate, resistivity change, and surface morphology characteristics were compared in the deposition temperature range of 400 °C–600 °C. While resistivity decreased to 177 µΩcm as the deposition temperature increased to 600 °C, an increase in surface roughness (Rq) to 0.69 nm and a deterioration in the step coverage were identified. In order to obtain a high-quality TiN thin film with excellent resistivity and step coverage characteristics even at low deposition temperatures, the TiN thin film was post-treated with plasma in a combination of N₂/He gas ratio of 3:2 to confirm the change in resistivity. X-ray diffraction analysis confirmed crystallization change in the TiN thin film caused by plasma energy. As a result, the resistivity of the TiN thin film deposited at 400 °C was confirmed to be lowered by about 25%. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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8 pages, 3627 KiB

Open AccessArticle

High Performance of InGaZnO TFTs Using Hf_xAl_yO_z Nanolaminates as Gate Insulators Prepared by ALD

by Chuanxin Huang, Yunyun Liu, Dianguo Ma, Zhongkai Guo, Haiyun Yao, Kaikai Lv, Zhongjun Tian, Lanju Liang, Ju Gao and Xingwei Ding

Coatings 2022, 12(12), 1811; https://doi.org/10.3390/coatings12121811 - 24 Nov 2022

Cited by 1 | Viewed by 1026

Abstract

In this study, Hf_xAl_yO_z nanolaminate, single-layer Al₂O₃, and HfO₂ gate insulators were fabricated by atomic layer deposition (ALD) to successfully integrate the InGaZnO (IGZO) thin-film transistors (TFTs). Compared with single-layer HfO₂-based [...] Read more.

In this study, Hf_xAl_yO_z nanolaminate, single-layer Al₂O₃, and HfO₂ gate insulators were fabricated by atomic layer deposition (ALD) to successfully integrate the InGaZnO (IGZO) thin-film transistors (TFTs). Compared with single-layer HfO₂-based TFTs, the Hf_xAl_yO_z-based IGZO TFTs showed a larger field-effect mobility of 10.31 cm²/Vs and a smaller subthreshold swing of 0.12 V/decade. Moreover, it showed a smaller threshold voltage shift of 0.5 V than that of HfO₂-based TFTs under gate-bias stress at +5 V for 900 s due to the smooth surface. Moreover, the high dielectric Hf_xAl_yO_z nanolaminate had a larger equivalent SiO₂ thinness than that of Al₂O₃ gate insulators, which are beneficial in applications of high-resolution display. Thus, the high mobility and high stability TFTs could be regarded as good candidates for active-matrix flat panel displays. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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13 pages, 3090 KiB

Open AccessProject Report

A Study on the Gap-Fill Process Deposited by the Deposition/Etch/Deposition Method in the Space-Divided PE-ALD System

by Baek-Ju Lee, Dong-Won Seo and Jae-Wook Choi

Coatings 2023, 13(1), 48; https://doi.org/10.3390/coatings13010048 - 27 Dec 2022

Cited by 1 | Viewed by 3881

Abstract

This study concerns the development of a gap-fill process technology for isolating trench patterns. There are various gap-filling techniques in the case of trench patterns; nevertheless, a processing technology adopting the DED (deposition/etch/deposition) method was developed in this study. After the etch step, [...] Read more.

This study concerns the development of a gap-fill process technology for isolating trench patterns. There are various gap-filling techniques in the case of trench patterns; nevertheless, a processing technology adopting the DED (deposition/etch/deposition) method was developed in this study. After the etch step, an Ar/O₂ (1:2) plasma treatment technology reduced the residual amount of F in the films to 0.05%. By improving the etch uniformity, the deposition uniformity after the DED process on a 12-inch flat wafer was secured within <1%, and a high-quality SiO₂ thin film with a dielectric constant of 3.97 and a breakdown field of 11.41 MV/cm was fabricated. The DED method can be used for gap-filling even in patterns with a high aspect ratio by changing process parameters, such as RF power and division of etch steps, according to the shape, depth, and CD size of the pattern. This study confirmed that a void-free gap-fill process can be developed in a trench pattern with a maximum aspect ratio of 40:1. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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