Design and Characterization of a Biocompatible Packaging Concept for Implantable Electronic Devices

A biocompatible packaging process for implantable electronic systems is described, combining biocompatibility and hermeticity with extreme miniaturization. In Phase 1 of the total packaging sequence, all chips are encapsulated in order to realize a bidirectional diffusion barrier, preventing body fluids from leaching into the package, which would cause corrosion, and preventing IC materials such as Cu from diffusing into the body, which would cause various adverse effects. For cost-effectiveness, this hermetic chip sealing is performed as a postprocessing step at the wafer level using modifications of standard clean room (CR) fabrication techniques. Well-known conductive and insulating CR materials are investigated with respect to their biocompatibility, diffusion barrier properties, and sensitivity to corrosion. In Phase 2 of the packaging process, all chips of the final device should be electrically connected, applying a biocompatible metallization scheme using, for example, gold or platinum. For electrodes in direct contact with the tissue after implantation, IrOx metallization is proposed. Phase 3 of device assembly is the final packaging step, during which all system components, such as electronics, passives, a battery, among others, will be interconnected. To provide sufficient mechanical support, all these components are embedded using a biocompatible elastomer such as PDMS.