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Open AccessArticle

Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO2/Al2O3/HfO2 Triple-Interlayer for Biomedical Implants

1
Centre for Microsystems Technology (CMST), imec and Ghent University, Technologiepark 126, 9052 Gent, Belgium
2
Pacific Northwest National Laboratory, Richland, WA 99352, USA
*
Authors to whom correspondence should be addressed.
Coatings 2019, 9(9), 579; https://doi.org/10.3390/coatings9090579
Received: 19 August 2019 / Revised: 8 September 2019 / Accepted: 10 September 2019 / Published: 12 September 2019
Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO2/Al2O3/HfO2 (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al2O3, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices. View Full-Text
Keywords: Al2O3; HfO2; polyimide; EIS; moisture barriers; lifetime; implantable medical devices Al2O3; HfO2; polyimide; EIS; moisture barriers; lifetime; implantable medical devices
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MDPI and ACS Style

Li, C.; Cauwe, M.; Yang, Y.; Schaubroeck, D.; Mader, L.; Op de Beeck, M. Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO2/Al2O3/HfO2 Triple-Interlayer for Biomedical Implants. Coatings 2019, 9, 579.

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