Conformal Hermetic Sealing of Wireless Microelectronic Implantable Chiplets by Multilayered Atomic Layer Deposition (ALD). (13th December 2018)

• Record Type: Journal Article
• Authors: Jeong, Joonsoo; Laiwalla, Farah; Lee, Jihun; Ritasalo, Riina; Pudas, Marko; Larson, Lawrence; Leung, Vincent; Nurmikko, Arto
• Is Part Of: Advanced functional materials. Volume 29:Number 5(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-12-13
• Subjects: atomic layer deposition -- hafnium oxide -- hermetic packaging -- neural implant -- neurograin; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201806440
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: A hermetic sealing method of sub‐millimeter‐sized microelectronic chiplets for wireless body implants is presented by ultrathin and electromagnetically transparent atomic layer deposition (ALD) coatings. Fully 3D conformal encapsulation of wirelessly powered microdevices is demonstrated both with and without opening windows for electrophysiological measurements. The chiplets embedding custom application‐specific integrated circuits (ASICs) with radio frequency (RF) transmitters are encapsulated by a stack of alternating layers of hafnium oxide and silicon dioxide to maximize impermeability of water and ionic penetration while minimizing the volume of the packaging material. The hermeticity of the devices is characterized through accelerated aging tests in saline at T = 87 °C, while continued functionality is monitored via evaluation of backscattered RF signals (near 1 GHz) to ascertain possible degradation and electronic failure. Earliest failures of wirelessly functional devices occur after more than 180 d of immersion at 87 °C. Wireless devices having opening windows through the ALD envelope show no signs of degradation for >100 d. This implies an equivalent lifetime >10 years at T = 37 °C. This approach is readily scalable to high throughput batch processing of hundreds of microchiplets, offering a methodology for hermetic packaging of microscale biomedical chronic implants. Abstract : A hermetic sealing method for protecting sub‐millimeter‐sized implantable microelectronic wireless chiplets against body fluids is developed by electromagnetically transparent, 3D conformal and ultrathin (≈100 nm) atomic layer deposition of multilayered HfO2 /SiO2 coatings. It is proven, by a series of accelerated aging tests mimicking the body environment, that this encapsulation scheme could provide reliable durability for >10 years in the body.