Biocompatible encapsulation and interconnection technology for implantable electronic devices

摘要

A biocompatible packaging process for implantable electronic systems is under development at imec, combining biocompatibility, hermeticity, extreme miniaturization and cost aspects. In a first phase of this packaging sequence, hermetic chip sealing is performed by encapsulating all chips to realize a bi-directional diffusion barrier preventing body fluids to leach into the package causing corrosion, and preventing IC materials such as Cu to diffuse into the body, causing various adverse effects. For cost effectiveness, this chip sealing is performed as post-processing at 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, biostability, diffusion barrier properties and sensitivity to corrosion. Material selection and integration aspects are modified until good properties are obtained. In a second phase of the packaging process, all chips of the final device should be electrically connected, applying a biocompatible metallization scheme. We selected the use of Pt due to its excellent biocompatibility and corrosion resistance. Since Pt is very expensive, a cost effective Pt-selective plating process is developed. During the third packaging step, all system components such as electronics, passives, a battery,... will be interconnected. To provide sufficient mechanical support, all components are finally embedded using a medical grade elastomer such as PDMS or Poly-urethane.