Thin, Transferred Layers of Silicon Dioxide and Silicon Nitride as Water and Ion Barriers for Implantable Flexible Electronic Systems

Thin, physically transferred layers of silicon dioxide (SiO2) thermally grown on the surfaces of silicon wafers offer excellent properties as long‐lived, hermetic biofluid barriers in flexible electronic implants. This paper explores materials and physics aspects of the transport of ions through the...

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Bibliographic Details
Published in:Advanced electronic materials 2017-08, Vol.3 (8), p.n/a
Main Authors: Song, Enming, Fang, Hui, Jin, Xin, Zhao, Jianing, Jiang, Chunsheng, Yu, Ki Jun, Zhong, Yiding, Xu, Dong, Li, Jinghua, Fang, Guanhua, Du, Haina, Zhang, Jize, Park, Jeong Min, Huang, Yonggang, Alam, Muhammad A., Mei, Yongfeng, Rogers, John A.
Format: Article
Language:English
Subjects:
flexible electronics
silicon dioxide
silicon nitride
thin film encapsulation
water/ion barrier
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Summary:Thin, physically transferred layers of silicon dioxide (SiO2) thermally grown on the surfaces of silicon wafers offer excellent properties as long‐lived, hermetic biofluid barriers in flexible electronic implants. This paper explores materials and physics aspects of the transport of ions through the SiO2 and the resultant effects on device performance and reliability. Accelerated soak tests of devices under electrical bias stress relative to a surrounding phosphate buffered saline (PBS) solution at a pH of 7.4 reveal the field dependence of these processes. Similar experimental protocols establish that coatings of SiNx on the SiO2 can block the passage of ions. Systematic experimental and theoretical investigations reveal the details associated with transport though this bilayer structure, and they serve as the basis for lifetime projections corresponding to more than a decade of immersion in PBS solution at 37 °C for the case of 100/200 nm of SiO2/SiNx. Temperature‐dependent simulations offer further understanding of two competing failure mechanisms—dissolution and ion diffusion—on device lifetime. These findings establish a basic physical understanding of effects that are essential to the stable operation of flexible electronics as chronic implants. A robust barrier impermeable to water and ions in biofluids with multidecade lifetimes is presented. This strategy combines a bilayer of SiNx formed by low‐pressure chemical vapor deposition and SiO2 formed by thermal growth on a silicon wafer with methods for their integration onto flexible bioelectronic platforms. The findings have broad relevance to a diverse range of biointegrated electronic devices.
ISSN:2199-160X
2199-160X
DOI:10.1002/aelm.201700077