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Lee S, Han G, Kim KH, Shim D, Go D, An J. High-Performance TiO 2/ZrO 2/TiO 2 Thin Film Capacitor by Plasma-Assisted Atomic Layer Annealing. ACS APPLIED MATERIALS & INTERFACES 2024; 16:34419-34427. [PMID: 38886188 DOI: 10.1021/acsami.4c06922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
Although laminate structures are widely used in electrostatic capacitors, unavoidable heterogeneous interfaces often deteriorate the dielectric properties by impeding film crystallization. In this study, a TiO2/ZrO2/TiO2 (TZT) laminate structure, where upper-TiO2 deposited on the heterogeneous interface was crystallized by plasma-assisted atomic layer annealing (ALA), was investigated. ALA effectively induced the phase transition of the upper-TiO2 from the amorphous or anatase phase to the rutile phase, leading to an increase in the dielectric constant, whereas the ZrO2 blocking interlayer maintained the amorphous phase owing to the extremely localized effect of ALA. Consequently, through the layer-by-layer phase control of ALA, the dielectric constant of the upper-TiO2 was enhanced by 25% by applying ALA, leading to an increase in a capacitance density of 27% of the TZT capacitor, whereas a low leakage current density of ∼10-8 A/cm2 was maintained (at 1 V). In addition, the TZT capacitor on three-dimensional structures (aspect ratio of 5:1) shows a high capacitance density of up to 461 nF/mm2 owing to ALA.
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Affiliation(s)
- Seunghyeon Lee
- Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul 01811, Republic of Korea
| | - Geongu Han
- Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul 01811, Republic of Korea
| | - Keun Hoi Kim
- Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul 01811, Republic of Korea
- Department of Nanofusion Research, National Nano Fab Center, Daejeon 34141, Republic of Korea
| | - Dongha Shim
- Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul 01811, Republic of Korea
| | - Dohyun Go
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Jihwan An
- Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul 01811, Republic of Korea
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyongsangbuk-do 37673, Republic of Korea
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2
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Beladiya V, Faraz T, Schmitt P, Munser AS, Schröder S, Riese S, Mühlig C, Schachtler D, Steger F, Botha R, Otto F, Fritz T, van Helvoirt C, Kessels WMM, Gargouri H, Szeghalmi A. Plasma-Enhanced Atomic Layer Deposition of HfO 2 with Substrate Biasing: Thin Films for High-Reflective Mirrors. ACS APPLIED MATERIALS & INTERFACES 2022; 14:14677-14692. [PMID: 35311275 DOI: 10.1021/acsami.1c21889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Tuning ion energies in plasma-enhanced atomic layer deposition (PEALD) processes enables fine control over the material properties of functional coatings. The growth, structural, mechanical, and optical properties of HfO2 thin films are presented in detail toward photonic applications. The influence of the film thickness and bias value on the properties of HfO2 thin films deposited at 100 °C using tetrakis(dimethylamino)hafnium (TDMAH) and oxygen plasma using substrate biasing is systematically analyzed. The HfO2 films deposited without a substrate bias show an amorphous microstructure with a low density, low refractive index, high incorporation of residual hydroxyl (OH) content, and high residual tensile stress. The material properties of HfO2 films significantly improved at a low bias voltage due to the interaction with oxygen ions accelerated to the film. Such HfO2 films have a higher density, higher refractive index, and lower residual OH incorporation than films without bias. The mechanical stress becomes compressive depending on the bias values. Further increasing the ion energies by applying a larger substrate bias results in a decrease of the film density, refractive index, and a higher residual OH incorporation as well as crystalline inclusions. The comparable material properties of the HfO2 films have been reported using tris(dimethylamino)cyclopentadienyl hafnium (TDMACpH) in a different apparatus, indicating that this approach can be transferred to various systems and is highly versatile. Finally, the substrate biasing technique has been introduced to deposit stress-compensated, crack- and delamination-free high-reflective (HR) mirrors at 355 and 532 nm wavelengths using HfO2 and SiO2 as high and low refractive index materials, respectively. Such mirrors could not be obtained without the substrate biasing during the deposition because of the high tensile stress of HfO2, leading to cracks in thick multilayer systems. An HR mirror for 532 nm wavelength shows a high reflectance of 99.93%, a residual transmittance of ∼530 ppm, and a low absorption of ∼11 ppm, as well as low scattering losses of ∼4 ppm, high laser-induced damage threshold, low mechanical stress, and high environmental stability.
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Affiliation(s)
- Vivek Beladiya
- Institute of Applied Physics, Friedrich Schiller University Jena, Albert-Einstein Str. 15, 07745 Jena, Germany
- Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, 07745 Jena, Germany
| | - Tahsin Faraz
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Paul Schmitt
- Institute of Applied Physics, Friedrich Schiller University Jena, Albert-Einstein Str. 15, 07745 Jena, Germany
- Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, 07745 Jena, Germany
| | - Anne-Sophie Munser
- Institute of Applied Physics, Friedrich Schiller University Jena, Albert-Einstein Str. 15, 07745 Jena, Germany
- Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, 07745 Jena, Germany
| | - Sven Schröder
- Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, 07745 Jena, Germany
| | | | - Christian Mühlig
- Leibniz-Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany
| | | | - Fabian Steger
- RhySearch, Werdenbergstrasse 4, 9471 Buchs, Switzerland
| | - Roelene Botha
- RhySearch, Werdenbergstrasse 4, 9471 Buchs, Switzerland
| | - Felix Otto
- Institute of Solid State Physics, Friedrich Schiller University Jena, Helmholtzweg 5, 07743 Jena, Germany
| | - Torsten Fritz
- Institute of Solid State Physics, Friedrich Schiller University Jena, Helmholtzweg 5, 07743 Jena, Germany
| | - Christian van Helvoirt
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Wilhelmus M M Kessels
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Hassan Gargouri
- Sentech Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany
| | - Adriana Szeghalmi
- Institute of Applied Physics, Friedrich Schiller University Jena, Albert-Einstein Str. 15, 07745 Jena, Germany
- Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, 07745 Jena, Germany
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3
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Arts K, Thepass H, Verheijen MA, Puurunen RL, Kessels WMM, Knoops HCM. Impact of Ions on Film Conformality and Crystallinity during Plasma-Assisted Atomic Layer Deposition of TiO 2. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2021; 33:5002-5009. [PMID: 34276135 PMCID: PMC8280614 DOI: 10.1021/acs.chemmater.1c00781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/15/2021] [Indexed: 05/03/2023]
Abstract
This work demonstrates that ions have a strong impact on the growth per cycle (GPC) and material properties during plasma-assisted atomic layer deposition (ALD) of TiO2 (titanium dioxide), even under mild plasma conditions with low-energy (<20 eV) ions. Using vertical trench nanostructures and microscopic cavity structures that locally block the flux of ions, it is observed that the impact of (low-energy) ions is an important factor for the TiO2 film conformality. Specifically, it is demonstrated that the GPC in terms of film thickness can increase by 20 to >200% under the influence of ions, which is correlated with an increase in film crystallinity and an associated strong reduction in the wet etch rate (in 30:1 buffered HF). The magnitude of the influence of ions is observed to depend on multiple parameters such as the deposition temperature, plasma exposure time, and ion energy, which may all be used to minimize or exploit this effect. For example, a relatively moderate influence of ions is observed at 200 °C when using short plasma steps and a grounded substrate, providing a low ion-energy dose of ∼1 eV nm-2 cycle-1, while a high effect is obtained when using extended plasma exposures or substrate biasing (∼100 eV nm-2 cycle-1). This work on TiO2 shows that detailed insight into the role of ions during plasma ALD is essential for precisely controlling the film conformality, material properties, and process reproducibility.
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Affiliation(s)
- Karsten Arts
- Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Harvey Thepass
- Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Marcel A Verheijen
- Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Eurofins Material Science, High Tech, Campus 11, 5656 AE Eindhoven, The Netherlands
| | - Riikka L Puurunen
- Aalto University School of Chemical Engineering, P.O. Box 16100, FI-00076 Aalto, Finland
| | - Wilhelmus M M Kessels
- Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Harm C M Knoops
- Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Oxford Instruments Plasma Technology, North End, Bristol BS49 4AP, United Kingdom
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4
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Legallais M, Mehdi H, David S, Bassani F, Labau S, Pelissier B, Baron T, Martinez E, Ghibaudo G, Salem B. Improvement of AlN Film Quality Using Plasma Enhanced Atomic Layer Deposition with Substrate Biasing. ACS APPLIED MATERIALS & INTERFACES 2020; 12:39870-39880. [PMID: 32805854 DOI: 10.1021/acsami.0c10515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In recent years, plasma enhanced atomic layer deposition (PEALD) has emerged as a key method for the growth of conformal and homogeneous aluminum nitride (AlN) films at the nanoscale. In this work, the utilized PEALD reactor was equipped not only with a traditional remote Inductively Coupled Plasma source but also with an innovative additional power supply connected to the substrate holder. Thus, we investigate here the substrate biasing effect on AlN film quality deposited on (100) silicon. We report that by adjusting the ion energy via substrate biasing, the AlN film quality can be significantly improved. Indeed, compared to films commonly deposited without bias, AlN deposited with a platen power of 5 W displays a 14% increase in the number of N-Al bonds according to X-ray spectroscopy analysis. Moreover, after having integrated them into Metal-AlN-Si capacitors, the 5 W AlN film exhibits a permittivity increase from 4.5 to 7.0 along with a drastic drop of leakage current density of more than 5 orders of magnitude. The use of substrate biasing during PEALD is thereby a promising strategy for the improvement of AlN film quality.
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Affiliation(s)
- Maxime Legallais
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Hussein Mehdi
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Sylvain David
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Franck Bassani
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Sébastien Labau
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Bernard Pelissier
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Thierry Baron
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
| | - Eugenie Martinez
- Université Grenoble Alpes, CEA/LETI, MINATEC Campus, F-38054 Grenoble, France
| | - Gérard Ghibaudo
- Université Grenoble Alpes, CNRS, Grenoble INP, IMEP-LAHC, 38000 Grenoble, France
| | - Bassem Salem
- Université Grenoble Alpes, CNRS, CEA/LETI Minatec, LTM, F-38054 Grenoble, France
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5
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Beladiya V, Becker M, Faraz T, Kessels WMME, Schenk P, Otto F, Fritz T, Gruenewald M, Helbing C, Jandt KD, Tünnermann A, Sierka M, Szeghalmi A. Effect of an electric field during the deposition of silicon dioxide thin films by plasma enhanced atomic layer deposition: an experimental and computational study. NANOSCALE 2020; 12:2089-2102. [PMID: 31912855 DOI: 10.1039/c9nr07202k] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The growth, chemical, structural, mechanical, and optical properties of oxide thin films deposited by plasma enhanced atomic layer deposition (PEALD) are strongly influenced by the average-bias voltage applied during the reaction step of surface functional groups with oxygen plasma species. Here, this effect is investigated thoroughly for SiO2 deposited in two different PEALD tools at average-bias voltages up to -300 V. Already at a very low average-bias voltage (< -10 V), the SiO2 films have significantly lower water content than films grown without biasing together with the formation of denser films having a higher refractive index and nearly stoichiometric composition. Substrate biasing during PEALD also enables control of mechanical stress. The experimental findings are supported by density functional theory and atomistic simulations. They demonstrate that the application of an electric field during the plasma step results in an increased energy transfer between energetic ions and the surface, directly influencing relevant surface reactions. Applying an electric field during the PEALD process leads to SiO2 thin films with significantly improved properties comparable to films grown by ion beam sputtering.
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Affiliation(s)
- Vivek Beladiya
- Institute of Applied Physics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany
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6
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Faraz T, Knoops HCM, Verheijen MA, van Helvoirt CAA, Karwal S, Sharma A, Beladiya V, Szeghalmi A, Hausmann DM, Henri J, Creatore M, Kessels WMM. Tuning Material Properties of Oxides and Nitrides by Substrate Biasing during Plasma-Enhanced Atomic Layer Deposition on Planar and 3D Substrate Topographies. ACS APPLIED MATERIALS & INTERFACES 2018; 10:13158-13180. [PMID: 29554799 PMCID: PMC5909180 DOI: 10.1021/acsami.8b00183] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Oxide and nitride thin-films of Ti, Hf, and Si serve numerous applications owing to the diverse range of their material properties. It is therefore imperative to have proper control over these properties during materials processing. Ion-surface interactions during plasma processing techniques can influence the properties of a growing film. In this work, we investigated the effects of controlling ion characteristics (energy, dose) on the properties of the aforementioned materials during plasma-enhanced atomic layer deposition (PEALD) on planar and 3D substrate topographies. We used a 200 mm remote PEALD system equipped with substrate biasing to control the energy and dose of ions by varying the magnitude and duration of the applied bias, respectively, during plasma exposure. Implementing substrate biasing in these forms enhanced PEALD process capability by providing two additional parameters for tuning a wide range of material properties. Below the regimes of ion-induced degradation, enhancing ion energies with substrate biasing during PEALD increased the refractive index and mass density of TiO x and HfO x and enabled control over their crystalline properties. PEALD of these oxides with substrate biasing at 150 °C led to the formation of crystalline material at the low temperature, which would otherwise yield amorphous films for deposition without biasing. Enhanced ion energies drastically reduced the resistivity of conductive TiN x and HfN x films. Furthermore, biasing during PEALD enabled the residual stress of these materials to be altered from tensile to compressive. The properties of SiO x were slightly improved whereas those of SiN x were degraded as a function of substrate biasing. PEALD on 3D trench nanostructures with biasing induced differing film properties at different regions of the 3D substrate. On the basis of the results presented herein, prospects afforded by the implementation of this technique during PEALD, such as enabling new routes for topographically selective deposition on 3D substrates, are discussed.
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Affiliation(s)
- Tahsin Faraz
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- E-mail:
| | - Harm C. M. Knoops
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Oxford
Instruments
Plasma Technology, North
End, Bristol, BS49 4AP, United Kingdom
| | - Marcel A. Verheijen
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Philips
Innovation Services, High Tech Campus 4, 5656 AE Eindhoven, The Netherlands
| | | | - Saurabh Karwal
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Akhil Sharma
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Vivek Beladiya
- Friedrich
Schiller University Jena, Albert-Einstein-Str. 13, 07745 Jena, Germany
| | - Adriana Szeghalmi
- Friedrich
Schiller University Jena, Albert-Einstein-Str. 13, 07745 Jena, Germany
- Fraunhofer Institute
for Applied Optics and Precision Engineering
IOF, Albert-Einstein-Str.
7, 07745 Jena, Germany
| | - Dennis M. Hausmann
- Lam
Research Corporation, 11155 SW Leveton Drive, Tualatin, Oregon 97062, United
States
| | - Jon Henri
- Lam
Research Corporation, 11155 SW Leveton Drive, Tualatin, Oregon 97062, United
States
| | - Mariadriana Creatore
- Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Low-Coherence Interferometric Fiber-Optic Sensors with Potential Applications as Biosensors. SENSORS 2017; 17:s17020261. [PMID: 28134855 PMCID: PMC5335988 DOI: 10.3390/s17020261] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/23/2017] [Accepted: 01/24/2017] [Indexed: 11/21/2022]
Abstract
Fiber-optic Fabry-Pérot interferometers (FPI) can be applied as optical sensors, and excellent measurement sensitivity can be obtained by fine-tuning the interferometer design. In this work, we evaluate the ability of selected dielectric thin films to optimize the reflectivity of the Fabry-Pérot cavity. The spectral reflectance and transmittance of dielectric films made of titanium dioxide (TiO2) and aluminum oxide (Al2O3) with thicknesses from 30 to 220 nm have been evaluated numerically and compared. TiO2 films were found to be the most promising candidates for the tuning of FPI reflectivity. In order to verify and illustrate the results of modelling, TiO2 films with the thickness of 80 nm have been deposited on the tip of a single-mode optical fiber by atomic layer deposition (ALD). The thickness, the structure, and the chemical properties of the films have been determined. The ability of the selected TiO2 films to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments, and to create multi-cavity interferometric sensors in FPI has then been studied. The presented sensor exhibits an ability to measure refractive index in the range close to that of silica glass fiber, where sensors without reflective films do not work, as was demonstrated by the measurement of the refractive index of benzene. This opens up the prospects of applying the investigated sensor in biosensing, which we confirmed by measuring the refractive index of hemoglobin and glucose.
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Chiappim W, Testoni GE, Doria ACOC, Pessoa RS, Fraga MA, Galvão NKAM, Grigorov KG, Vieira L, Maciel HS. Relationships among growth mechanism, structure and morphology of PEALD TiO2 films: the influence of O2 plasma power, precursor chemistry and plasma exposure mode. NANOTECHNOLOGY 2016; 27:305701. [PMID: 27302656 DOI: 10.1088/0957-4484/27/30/305701] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Titanium dioxide (TiO2) thin films have generated considerable interest over recent years, because they are functional materials suitable for a wide range of applications. The efficient use of the outstanding functional properties of these films relies strongly on their basic characteristics, such as structure and morphology, which are affected by deposition parameters. Here, we report on the influence of plasma power and precursor chemistry on the growth kinetics, structure and morphology of TiO2 thin films grown on Si(100) by plasma-enhanced atomic layer deposition (PEALD). For this, remote capacitively coupled 13.56 MHz oxygen plasma was used to act as a co-reactant during the ALD process using two different metal precursors: titanium tetrachloride (TiCl4) and titanium tetraisopropoxide (TTIP). Furthermore, we investigate the effect of direct plasma exposure during the co-reactant pulse on the aforementioned material properties. The extensive characterization of TiO2 films using Rutherford backscattering spectroscopy, ellipsometry, x-ray diffraction (XRD), field-emission scanning electron microscopy, and atomic force microscopy (AFM) have revealed how the investigated process parameters affect their growth per cycle (GPC), crystallization and morphology. The GPC tends to increase with plasma power for both precursors, however, for the TTIP precursor, it starts decreasing when the plasma power is greater than 100 W. From XRD analysis, we found a good correlation between film crystallinity and GPC behavior, mainly for the TTIP process. The AFM images indicated the formation of films with grain size higher than film thickness (grain size/film thickness ratio ≈20) for both precursors, and plasma power analysis allows us to infer that this phenomenon can be directly related to the increase of the flux of energetic oxygen species on the substrate/growing film surface. Finally, the effect of direct plasma exposure on film structure and morphology was evidenced showing that the grid removal causes a drastic reduction in the grain size, particularly for TiO2 synthesized using TiCl4.
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Affiliation(s)
- W Chiappim
- Nanotechnology and Plasmas Processes Laboratory, Universidade do Vale do Paraíba (Univap), São José dos Campos, SP, 12244-000, Brazil. Plasma and Processes Laboratory, Instituto Tecnológico de Aeronáutica (ITA-DCTA), São José dos Campos, SP, 12228-900, Brazil
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9
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Ratzsch S, Kley EB, Tünnermann A, Szeghalmi A. Inhibition of Crystal Growth during Plasma Enhanced Atomic Layer Deposition by Applying BIAS. MATERIALS 2015; 8:7805-7812. [PMID: 28793679 PMCID: PMC5458875 DOI: 10.3390/ma8115425] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/09/2015] [Accepted: 11/12/2015] [Indexed: 11/16/2022]
Abstract
In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO2) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)4 as metal organic precursor. Oxygen plasma, provided by remote inductively coupled plasma, was used as an oxygen source. The TiO2 films were deposited with and without DC biasing. A strong dependence of the applied voltage on the formation of crystallites in the TiO2 layer is shown. These crystallites form spherical hillocks on the surface which causes high surface roughness. By applying a higher voltage than the plasma potential no hillock appears on the surface. Based on these results, it seems likely, that ions are responsible for the nucleation and hillock growth. Hence, the hillock formation can be controlled by controlling the ion energy and ion flux. The growth per cycle remains unchanged, whereas the refractive index slightly decreases in the absence of energetic oxygen ions.
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Affiliation(s)
- Stephan Ratzsch
- Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, Max Wien Platz 1, Jena 07743, Germany.
| | - Ernst-Bernhard Kley
- Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, Max Wien Platz 1, Jena 07743, Germany.
| | - Andreas Tünnermann
- Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, Max Wien Platz 1, Jena 07743, Germany.
- Fraunhofer-Institut für Angewandte Optik und Feinmechanik, Albert-Einstein-Str. 7, Jena 07745, Germany.
| | - Adriana Szeghalmi
- Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, Max Wien Platz 1, Jena 07743, Germany.
- Fraunhofer-Institut für Angewandte Optik und Feinmechanik, Albert-Einstein-Str. 7, Jena 07745, Germany.
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Ratzsch S, Kley EB, Tünnermann A, Szeghalmi A. Influence of the oxygen plasma parameters on the atomic layer deposition of titanium dioxide. NANOTECHNOLOGY 2015; 26:024003. [PMID: 25525676 DOI: 10.1088/0957-4484/26/2/024003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The influence of the oxygen plasma parameters on the morphology and optical properties of TiO2 thin films has been extensively analyzed in plasma enhanced atomic layer deposition (PEALD) processes. Crystalline aggregates with the anatase phase have been identified on the film surface at a low deposition temperature (down to 70 °C) under specific plasma conditions. Up to 70% surface coverage by anatase crystallites is obtained at low oxygen gas flow rates and high plasma power. The hillocks abundance is correlated with high ion flux and electron density and with the resulting enhanced ion bombardment of the surface. Altering the plasma conditions is an important parameter besides temperature to control the morphology of the titania film for specific applications such as photocatalysis or functional optical coatings. Specifically, photocatalytic titania coatings on polymer substrates could benefit of such low temperature PEALD processes with abundant anatase crystallites; whereas optical coatings require smooth, high refractive index titania as obtained with low plasma power and high oxygen flow rate.
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Affiliation(s)
- Stephan Ratzsch
- Institut für Angewandte Physik, Friedrich-Schiller-Universität Jena, Max Wien Platz 1, D-07743 Jena, Germany
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11
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Potts S, Kessels W. Energy-enhanced atomic layer deposition for more process and precursor versatility. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2013.06.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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