title: Development of Pinhole-Free Amorphous Aluminum Oxide Protective Layers for Biomedical Device Applications.
abstract: This paper describes synthesis of ultrathin pinhole-free insulating aluminum oxide layers for electronic device protection in corrosive liquid environments, such as phosphate buffered saline (PBS) or clinical fluids, to enable emerging biomedical applications such as biomolecular sensors. A pinhole-free 25-nm thick amorphous aluminum oxide layer has been achieved using ultra-high vacuum DC magnetron reactive sputtering of aluminum in oxygen/argon plasma followed by oxygen plasma post-processing. Deposition parameters were optimized to achieve the best corrosion protection of lithographically defined device structures. Electrochemical deposition of copper through the aluminum oxide layers was used to detect the presence (or absence) of pinholes. FTIR, XPS, and spectroscopic ellipsometry were used to characterize the material properties of the protective layers. Electrical resistance of the copper device structures protected by the aluminum oxide layers and exposed to a PBS solution was used as a metric to evaluate the long-term stability of these device structures.
authors.affiliation: Biomedical Engineering, University of Houston, Houston, Texas 77204.
authors.forename: Julia
authors.initials: J
authors.lastname: Litvinov
authors.forename: Yi-Ju
authors.initials: YJ
authors.lastname: Wang
authors.forename: Jinnie
authors.initials: J
authors.lastname: George
authors.forename: Pawilai
authors.initials: P
authors.lastname: Chinwangso
authors.forename: Stanko
authors.initials: S
authors.lastname: Brankovic
authors.forename: Richard C
authors.initials: RC
authors.lastname: Willson
authors.forename: Dmitri
authors.initials: D
authors.lastname: Litvinov
keywords: DC magnetron sputtering; aluminum oxide; biosensor; corrosion; ultrathin coating