Design and fabrication of stiff silicon probes: A step towards sophisticated cochlear implant electrodes

Cochlear implants work on the principle of direct electrical stimulation of the auditory nerve. It has advantages to replace their traditional wired electrodes by a high-density thin-film multielectrode stimulation array which is relatively small in dimensions, stable, resistant to electrolysis, and offers batch fabrication capabilities with good electrical and mechanical properties. In this paper a development review of cochlear implants (CI's) along with the fabrication of stiff silicon probes using silicon micromachining is described. The initial design for a new microelectrode array is described with microfabrication steps for stiff silicon probes which is a step towards a future flexible CI-electrodes. These stiff probes were fabricated in order to study the problems involved in fabrication and the behaviour of the probes when inserted perpendicular to the auditory nerve. The probes were fabricated with lengths ranging from 3.5 mm to 10.5 mm with thickness between 60 to 70 microns