Ion Penetration Model of SiO2/SiNx/SiO2 Barrier Trilayer for Implantable Electronics

Wearable and implantable electronic (WIE) devices have found widespread applications in real-time health monitoring systems. Materials in flexible, thin film form that can serve as long-lived barriers to biofluid penetration are essential to the development of chronic biomedical implants. Ions in biofluids (such as Na
⁺
) that diffuse through the encapsulation layer can adversely affect the performance of the entire system. In this work, we have conducted systematic theoretical simulations on the ion-diffusion behaviors of combinations of silicon oxides and nitrides. Alternating dielectric layers of SiO
₂
/SiN
_x
/SiO
₂
have been proven to effectively retard ion transport compared with the single or bilayer films. Our numerical model serves as the prediction of ion diffusion induced threshold voltage shift which is the basis for lifetime projection for MOSFET-based biomedical implants.