Low-temperature atomic layer deposition of indium oxide thin films using trimethylindium and oxygen plasma

Indium oxide (InxOy) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) using trimethylindium and oxygen plasma in a low-temperature range of 80–200 °C. The optical properties, chemical composition, crystallographic structure, and electrical characteristics of these layers...

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Veröffentlicht in:Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2021-12, Vol.39 (6)
Hauptverfasser: Mahmoodinezhad, Ali, Morales, Carlos, Naumann, Franziska, Plate, Paul, Meyer, Robert, Janowitz, Christoph, Henkel, Karsten, Kot, Małgorzata, Zoellner, Marvin Hartwig, Wenger, Christian, Flege, Jan Ingo
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Sprache:eng
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Zusammenfassung:Indium oxide (InxOy) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) using trimethylindium and oxygen plasma in a low-temperature range of 80–200 °C. The optical properties, chemical composition, crystallographic structure, and electrical characteristics of these layers were investigated by spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), as well as current-voltage and capacitance-voltage measurements. The SE results yielded a nearly constant growth rate of 0.56 Å per cycle and a thickness inhomogeneity of ≤1.2% across 4-in. substrates in the temperature range of 100–150 °C. The refractive index (at 632.8 nm) was found to be 2.07 for the films deposited at 150 °C. The PEALD-InxOy layers exhibit a direct (3.3 ± 0.2 eV) and an indirect (2.8 ± 0.1 eV) bandgap with an uptrend for both with increasing substrate temperature. Based on XPS characterization, all InxOy samples are free of carbon impurities and show a temperature-dependent off-stoichiometry indicating oxygen vacancies. XRD diffraction patterns demonstrate an onset of crystallization at 150 °C. Consistent with the optical, XPS, and XRD data, the films deposited at ≥150 °C possess higher electrical conductivity. Our findings prove that a low-temperature PEALD process of InxOy is feasible and promising for a high-quality thin-film deposition without chemical impurities on thermally fragile substrates.
ISSN:0734-2101
1520-8559
DOI:10.1116/6.0001375