Chemically Stable Atomic-Layer-Deposited Al2O3 Films for Processability

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Chemically Stable Atomic-Layer-Deposited Al2O3 Films for Processability. / Broas, Mikael; Kanninen, Olli; Vuorinen, Vesa; Tilli, Markku; Paulasto-Kröckel, Mervi.

In: ACS Omega, Vol. 2, No. 7, 31.07.2017, p. 3390-3398.

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Broas, Mikael ; Kanninen, Olli ; Vuorinen, Vesa ; Tilli, Markku ; Paulasto-Kröckel, Mervi. / Chemically Stable Atomic-Layer-Deposited Al2O3 Films for Processability. In: ACS Omega. 2017 ; Vol. 2, No. 7. pp. 3390-3398.

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@article{ebb6478bab8f42879048e4bf948514fc,
title = "Chemically Stable Atomic-Layer-Deposited Al2O3 Films for Processability",
abstract = "Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause cross-contamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate-film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al-O-Si interfacial layer.",
keywords = "crystal structure, deposition process, heat treatment, microstructure, optical properties, phase transition, surface reaction, surface structure",
author = "Mikael Broas and Olli Kanninen and Vesa Vuorinen and Markku Tilli and Mervi Paulasto-Kr{\"o}ckel",
year = "2017",
month = "7",
day = "31",
doi = "10.1021/acsomega.7b00443",
language = "English",
volume = "2",
pages = "3390--3398",
journal = "ACS Omega",
issn = "2470-1343",
publisher = "AMERICAN CHEMICAL SOCIETY",
number = "7",

}

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TY - JOUR

T1 - Chemically Stable Atomic-Layer-Deposited Al2O3 Films for Processability

AU - Broas, Mikael

AU - Kanninen, Olli

AU - Vuorinen, Vesa

AU - Tilli, Markku

AU - Paulasto-Kröckel, Mervi

PY - 2017/7/31

Y1 - 2017/7/31

N2 - Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause cross-contamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate-film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al-O-Si interfacial layer.

AB - Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause cross-contamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate-film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al-O-Si interfacial layer.

KW - crystal structure

KW - deposition process

KW - heat treatment

KW - microstructure

KW - optical properties

KW - phase transition

KW - surface reaction

KW - surface structure

UR - http://www.scopus.com/inward/record.url?scp=85028918512&partnerID=8YFLogxK

U2 - 10.1021/acsomega.7b00443

DO - 10.1021/acsomega.7b00443

M3 - Article

VL - 2

SP - 3390

EP - 3398

JO - ACS Omega

JF - ACS Omega

SN - 2470-1343

IS - 7

ER -

ID: 15747251