Research

10 pages, 3602 KiB

Open AccessArticle

Microstructures of HfO_x Films Prepared via Atomic Layer Deposition Using La(NO₃)₃·6H₂O Oxidants

by Seon Yong Kim, Yong Chan Jung, Sejong Seong, Taehoon Lee, In-Sung Park and Jinho Ahn

Materials 2021, 14(23), 7478; https://doi.org/10.3390/ma14237478 - 06 Dec 2021

Cited by 5 | Viewed by 2051

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as [...] Read more.

Hafnium oxide (HfO_x) films have a wide range of applications in solid-state devices, including metal–oxide–semiconductor field-effect transistors (MOSFETs). The growth of HfO_x films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO₃)₃·6H₂O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfO_x films deposited using a conventional oxidant (H₂O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200–350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H₂O. HfO_x films deposited using the LNS oxidant had smaller crystallites than those deposited using H₂O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfO_x films deposited using LNS and H₂O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

12 pages, 5178 KiB

Open AccessArticle

Chemical Reaction and Ion Bombardment Effects of Plasma Radicals on Optoelectrical Properties of SnO₂ Thin Films via Atomic Layer Deposition

by Pao-Hsun Huang, Zhi-Xuan Zhang, Chia-Hsun Hsu, Wan-Yu Wu, Chien-Jung Huang and Shui-Yang Lien

Materials 2021, 14(3), 690; https://doi.org/10.3390/ma14030690 - 02 Feb 2021

Cited by 9 | Viewed by 2972

Abstract

In this study, the effect of radical intensity on the deposition mechanism, optical, and electrical properties of tin oxide (SnO₂) thin films is investigated. The SnO₂ thin films are prepared by plasma-enhanced atomic layer deposition with different plasma power from [...] Read more.

In this study, the effect of radical intensity on the deposition mechanism, optical, and electrical properties of tin oxide (SnO₂) thin films is investigated. The SnO₂ thin films are prepared by plasma-enhanced atomic layer deposition with different plasma power from 1000 to 3000 W. The experimental results show that plasma contains different amount of argon radicals (Ar*) and oxygen radicals (O*) with the increased power. The three deposition mechanisms are indicated by the variation of Ar* and O* intensities evidenced by optical emission spectroscopy. The adequate intensities of Ar* and O* are obtained by the power of 1500 W, inducing the highest oxygen vacancies (O_V) ratio, the narrowest band gap, and the densest film structure. The refractive index and optical loss increase with the plasma power, possibly owing to the increased film density. According to the Hall effect measurement results, the improved plasma power from 1000 to 1500 W enhances the carrier concentration due to the enlargement of O_V ratio, while the plasma powers higher than 1500 W further cause the removal of O_V and the significant bombardment from Ar*, leading to the increase of resistivity. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

15 pages, 3139 KiB

Open AccessArticle

Characterization of Electrical Traps Formed in Al₂O₃ under Various ALD Conditions

by Md. Mamunur Rahman, Ki-Yong Shin and Tae-Woo Kim

Materials 2020, 13(24), 5809; https://doi.org/10.3390/ma13245809 - 19 Dec 2020

Cited by 8 | Viewed by 2262

Abstract

Frequency dispersion in the accumulation region seen in multifrequency capacitance–voltage characterization, which is believed to be caused mainly by border traps, is a concerning issue in present-day devices. Because these traps are a fundamental property of oxides, their formation is expected to be [...] Read more.

Frequency dispersion in the accumulation region seen in multifrequency capacitance–voltage characterization, which is believed to be caused mainly by border traps, is a concerning issue in present-day devices. Because these traps are a fundamental property of oxides, their formation is expected to be affected to some extent by the parameters of oxide growth caused by atomic layer deposition (ALD). In this study, the effects of variation in two ALD conditions, deposition temperature and purge time, on the formation of near-interfacial oxide traps in the Al₂O₃ dielectric are examined. In addition to the evaluation of these border traps, the most commonly examined electrical traps—i.e., interface traps—are also investigated along with the hysteresis, permittivity, reliability, and leakage current. The results reveal that a higher deposition temperature helps to minimize the formation of border traps and suppress leakage current but adversely affects the oxide/semiconductor interface and the permittivity of the deposited film. In contrast, a longer purge time provides a high-quality atomic-layer-deposited film which has fewer electrical traps and reasonable values of permittivity and breakdown voltage. These findings indicate that a moderate ALD temperature along with a sufficiently long purge time will provide an oxide film with fewer electrical traps, a reasonable permittivity, and a low leakage current. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

10 pages, 4161 KiB

Open AccessArticle

Comparative Study of Pd/B₄C X-ray Multilayer Mirrors Fabricated by Magnetron Sputtering with Kr and Ar Gas

by Hangjian Ni, Qiushi Huang, Genchang Liu, Runze Qi, Zhong Zhang, Xiuhong Li, Zhongliang Li, Jie Wang and Zhanshan Wang

Materials 2020, 13(20), 4504; https://doi.org/10.3390/ma13204504 - 11 Oct 2020

Cited by 11 | Viewed by 1883

Abstract

Ultrathin Pd/B₄C multilayers are suitable X-ray mirrors working at the photon energy region of 7–20 keV. To further improve the layer structure, Pd/B₄C multilayers with a d-spacing of 2.5 nm were fabricated by magnetron sputtering using the heavy noble [...] Read more.

Ultrathin Pd/B₄C multilayers are suitable X-ray mirrors working at the photon energy region of 7–20 keV. To further improve the layer structure, Pd/B₄C multilayers with a d-spacing of 2.5 nm were fabricated by magnetron sputtering using the heavy noble gas Kr and compared with the conventional ones fabricated by Ar. Although the Kr-sputtering process can work at a lower pressure, the interface width—especially the interface roughness—is a little larger than that made by Ar. A stronger polycrystallization and a lower content of sputter gas atoms were found in the Kr-made sample, which can be explained by the joint effect from less recoiled particles and lower sputtering pressure. A good reflectance of 68% of the Kr made multilayer was measured at 10 keV, which is only slightly lower than that of the Ar made sample (71%). Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

10 pages, 3132 KiB

Open AccessArticle

Low Temperature Thermal Atomic Layer Deposition of Aluminum Nitride Using Hydrazine as the Nitrogen Source

by Yong Chan Jung, Su Min Hwang, Dan N. Le, Aswin L. N. Kondusamy, Jaidah Mohan, Sang Woo Kim, Jin Hyun Kim, Antonio T. Lucero, Arul Ravichandran, Harrison Sejoon Kim, Si Joon Kim, Rino Choi, Jinho Ahn, Daniel Alvarez, Jeff Spiegelman and Jiyoung Kim

Materials 2020, 13(15), 3387; https://doi.org/10.3390/ma13153387 - 31 Jul 2020

Cited by 13 | Viewed by 4850

Abstract

Aluminum nitride (AlN) thin films were grown using thermal atomic layer deposition in the temperature range of 175–350 °C. The thin films were deposited using trimethyl aluminum (TMA) and hydrazine (N₂H₄) as a metal precursor and nitrogen source, respectively. [...] Read more.

Aluminum nitride (AlN) thin films were grown using thermal atomic layer deposition in the temperature range of 175–350 °C. The thin films were deposited using trimethyl aluminum (TMA) and hydrazine (N₂H₄) as a metal precursor and nitrogen source, respectively. Highly reactive N₂H₄, compared to its conventionally used counterpart, ammonia (NH₃), provides a higher growth per cycle (GPC), which is approximately 2.3 times higher at a deposition temperature of 300 °C and, also exhibits a low impurity concentration in as-deposited films. Low temperature AlN films deposited at 225 °C with a capping layer had an Al to N composition ratio of 1:1.1, a close to ideal composition ratio, with a low oxygen content (7.5%) while exhibiting a GPC of 0.16 nm/cycle. We suggest that N₂H₄ as a replacement for NH₃ is a good alternative due to its stringent thermal budget. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

8 pages, 2595 KiB

Open AccessFeature PaperArticle

A Comprehensive Study on the Effect of TiN Top and Bottom Electrodes on Atomic Layer Deposited Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films

by Si Joon Kim, Jaidah Mohan, Harrison Sejoon Kim, Su Min Hwang, Namhun Kim, Yong Chan Jung, Akshay Sahota, Kihyun Kim, Hyun-Yong Yu, Pil-Ryung Cha, Chadwin D. Young, Rino Choi, Jinho Ahn and Jiyoung Kim

Materials 2020, 13(13), 2968; https://doi.org/10.3390/ma13132968 - 02 Jul 2020

Cited by 31 | Viewed by 5932

Abstract

The discovery of ferroelectricity in HfO₂-based materials in 2011 provided new research directions and opportunities. In particular, for atomic layer deposited Hf_0.5Zr_0.5O₂ (HZO) films, it is possible to obtain homogenous thin films with satisfactory ferroelectric properties [...] Read more.

The discovery of ferroelectricity in HfO₂-based materials in 2011 provided new research directions and opportunities. In particular, for atomic layer deposited Hf_0.5Zr_0.5O₂ (HZO) films, it is possible to obtain homogenous thin films with satisfactory ferroelectric properties at a low thermal budget process. Based on experiment demonstrations over the past 10 years, it is well known that HZO films show excellent ferroelectricity when sandwiched between TiN top and bottom electrodes. This work reports a comprehensive study on the effect of TiN top and bottom electrodes on the ferroelectric properties of HZO thin films (10 nm). Investigations showed that during HZO crystallization, the TiN bottom electrode promoted ferroelectric phase formation (by oxygen scavenging) and the TiN top electrode inhibited non-ferroelectric phase formation (by stress-induced crystallization). In addition, it was confirmed that the TiN top and bottom electrodes acted as a barrier layer to hydrogen diffusion into the HZO thin film during annealing in a hydrogen-containing atmosphere. These features make the TiN electrodes a useful strategy for improving and preserving the ferroelectric properties of HZO thin films for next-generation memory applications. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

10 pages, 2702 KiB

Open AccessArticle

Structural, Optical and Electrical Properties of HfO₂ Thin Films Deposited at Low-Temperature Using Plasma-Enhanced Atomic Layer Deposition

by Kyoung-Mun Kim, Jin Sub Jang, Soon-Gil Yoon, Ju-Young Yun and Nak-Kwan Chung

Materials 2020, 13(9), 2008; https://doi.org/10.3390/ma13092008 - 25 Apr 2020

Cited by 40 | Viewed by 8047

Abstract

HfO₂ was deposited at 80–250 °C by plasma-enhanced atomic layer deposition (PEALD), and properties were compared with those obtained by using thermal atomic layer deposition (thermal ALD). The ALD window, i.e., the region where the growth per cycle (GPC) is constant, shifted [...] Read more.

HfO₂ was deposited at 80–250 °C by plasma-enhanced atomic layer deposition (PEALD), and properties were compared with those obtained by using thermal atomic layer deposition (thermal ALD). The ALD window, i.e., the region where the growth per cycle (GPC) is constant, shifted from high temperatures (150–200 °C) to lower temperatures (80–150 °C) in PEALD. HfO₂ deposited at 80 °C by PEALD showed higher density (8.1 g/cm³) than those deposited by thermal ALD (5.3 g/cm³) and a smooth surface (RMS Roughness: 0.2 nm). HfO₂ deposited at a low temperature by PEALD showed decreased contaminants compared to thermal ALD deposited HfO₂. Values of refractive indices and optical band gap of HfO₂ deposited at 80 °C by PEALD (1.9, 5.6 eV) were higher than those obtained by using thermal ALD (1.7, 5.1 eV). Transparency of HfO₂ deposited at 80 °C by PEALD on polyethylene terephthalate (PET) was high (> 84%). PET deposited above 80 °C was unable to withstand heat and showed deformation. HfO₂ deposited at 80 °C by PEALD showed decreased leakage current from 1.4 × 10⁻² to 2.5 × 10⁻⁵ A/cm² and increased capacitance of approximately 21% compared to HfO₂ using thermal ALD. Consequently, HfO₂ deposited at a low temperature by PEALD showed improved properties compared to HfO₂ deposited by thermal ALD. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

11 pages, 1833 KiB

Open AccessArticle

Plasma Enhanced Atomic Layer Deposition of Plasmonic TiN Ultrathin Films Using TDMATi and NH₃

by Katherine Hansen, Melissa Cardona, Amartya Dutta and Chen Yang

Materials 2020, 13(5), 1058; https://doi.org/10.3390/ma13051058 - 27 Feb 2020

Cited by 12 | Viewed by 4072

Abstract

Transition metal nitrides, like titanium nitride (TiN), are promising alternative plasmonic materials. Here we demonstrate a low temperature plasma-enhanced atomic layer deposition (PE-ALD) of non-stoichiometric TiN_0.71 on lattice-matched and -mismatched substrates. The TiN was found to be optically metallic for both thick [...] Read more.

Transition metal nitrides, like titanium nitride (TiN), are promising alternative plasmonic materials. Here we demonstrate a low temperature plasma-enhanced atomic layer deposition (PE-ALD) of non-stoichiometric TiN_0.71 on lattice-matched and -mismatched substrates. The TiN was found to be optically metallic for both thick (42 nm) and thin (11 nm) films on MgO and Si <100> substrates, with visible light plasmon resonances in the range of 550–650 nm. We also demonstrate that a hydrogen plasma post-deposition treatment improves the metallic quality of the ultrathin films on both substrates, increasing the ε₁ slope by 1.3 times on MgO and by 2 times on Si (100), to be similar to that of thicker, more metallic films. In addition, this post-deposition was found to tune the plasmonic properties of the films, resulting in a blue-shift in the plasmon resonance of 44 nm on a silicon substrate and 59 nm on MgO. Full article

(This article belongs to the Special Issue Atomic Layer Deposition Technique in Material Science)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Atomic Layer Deposition Technique in Material Science

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI