Fabrication of iridium oxide neural electrodes at the wafer level

Electro-deposition, electrical activation, thermal oxidation, and reactive ion sputtering are the four primary methods to fabricate iridium oxide film. Among these methods, reactive ion sputtering is a commonly used method in standard micro-fabrication processes. In different sputtering conditions, the component, texture, and electrochemistry character of iridium oxide varies considerably. To fabricate the iridium oxide film compatible with the wafer-level processing of neural electrodes, the quality of iridium oxide film must be able to withstand the mechanical and chemical impact of post-processing, and simultaneously achieve good performance as a neural electrode. In this study, parameters of sputtering were researched and developed to achieve a balance between mechanical stability and good electrochemical characteristics of iridium oxide film on electrode. Iridium oxide fabricating process combined with fabrication flow of silicon electrodes, at wafer-level, is introduced to produce silicon based planar iridium oxide neural electrodes. Compared with bare gold electrodes, iridium oxide electrodes fabricated with this method exhibit particularly good electrochemical stability, low impedance of 386 kΩ at 1 kHz, high safe charge storage capacity of 3.2 mC/cm², and good impedance consistency of less than 25% fluctuation.