Recessed Traces for Planarized Passivation of Chronic Neural Microelectrodes

Implantable microfabricated neural electrodes have numerous neuroscientific research and clinical applications. However, these devices are prone to failure after several months in vivo. One mechanism is failure of passivation layers followed by corrosion of metal traces in the saline environment. It has been suggested that mechanical stress accelerates passivation layer failure and that stress is concentrated whenever passivation layers have a non-planar topography. Therefore, we developed a simple process for recessing metal traces within the substrate so that overlying passivation layers are planar. The process requires no extra masks and no post-passivation planarization steps.