Recessed Traces for Planarized Passivation of Chronic Neural Microelectrodes

Abstract

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.

Unprotected sidewalls of implantable silicon-based neural probes and conformal coating as a solution

“…Future work will compare these results with standard accelerating aging tests results and validate the ALD protection technique in a long-term in vivo functional study. Figure 5 shows an overview of the microfabrication process which was part of a previously in vivo-validated device technology 12,13,[44][45][46][47][48] . Four groups of devices were fabricated in this study: control (no protection), ALD-SiO 2 , ICPCVD-SiO 2 , and both ALD-and ICPCVD-SiO 2 .…”

Advances in Soft Bioelectronics for Brain Research and Clinical Neuroengineering

“…20 The vigorous micromotions of the brain also cause chronic stress on the tissue. 21,22 Moreover, the mechanical stress on the implanted electrode can lead to a failure of the encapsulation layer, causing electrical current to leak to non-targeted brain regions 23 and making the electrodes vulnerable to corrosion.…”

Fabrication and modeling of recessed traces for silicon-based neural microelectrodes

“…We successfully incorporated the technique into our production process for functional probes, similar to those we have used extensively in long-term animal studies [12,13]. We previously described our method in a short conference publication [33]. In this report, we provide greater detail on the method and its optimization and use finite element modeling to show its predicted effect on intrinsic stress.…”

“…We successfully incorporated the technique into our fabrication process for functional probes, similar to those we have used extensively in long-term animal studies [12,13]. We previously described our method in a short conference publication [33]. In this report, we provide greater detail on the method, perform finite element modeling to show the predicted effect on intrinsic stress, and provide extensive electrochemical validation to show that recessed devices have recording and stimulation capabilities comparable to an established non-recessed device design.…”