Microelectrode arrays for neurostimulation fabricated by integrated circuit technology

We are engaged at Stanford University in the development of an auditory prosthesis which works by direct electrical stimulation of the auditory nerve. This project must confront many questions on the nature of speech processing, speech comprehension, and the representation of speech as electrical stimulation patterns on the auditory nerve. It is also necessary to develop a microelectrode array for delivery of the appropriate electrical stimulation pattern onto the auditory nerve. While it is possible both in principle and practice to fabricate such arrays using fine wire bundles, it is clearly attractive to utilize the high‐resolution high‐precision photolithographic technology common to integrated circuit fabrication to achieve arrays which are electrically and mechanically optimal and are reproducible and stable. For the cochlear prosthesis we have developed rigid electrode arrays using a sapphire substrate, tantalum conductors, platinum electrodes and tantalum pentoxide and silicon nitride insulation. We have also developed a flexible electrode array using a liquid polymer and platinum conductors. Comments will be made on problems solved in developing these fabrication techniques and on their extensibility to electrodes for other biostimulation applications.