New Design of the Cochlear Implant Probe with Polycrystalline Diamond Piezoresistive Position Sensors

Polycrystalline diamond (poly-C) was used as a piezoresistive position sensor in a cochlear implant probe for its high piezoresistive sensitivity. Based on previous studies [Spelman, FA, 1999], the 3rd generation cochlear probe with poly-C position sensors were designed and fabricated with several new improvements for compatibility and integration with the Si-based bulk micromachining technology. In-situ doped poly-C film, with a thickness of 2 mum, were grown and patterned on the probe as the piezoresistor. Low contact resistivity between poly-C and metal was achieved using a highly doped poly-C thin interlayer. A piezoresistive gauge factor of 44 was achieved from the poly-C sensor on the probe. The film quality, electrical properties, contact resistance and piezoresistivity of the poly-C sensors were characterized, which demonstrated a successful integration of diamond technology with the silicon based microsystem