Study of polycrystalline diamond piezoresistive position sensors for application in cochlear implant probe

Polycrystalline diamond (poly-C) piezoresistive sensors, with high sensitivity, were fabricated and tested for the purpose of integration with Si-based microsystems. The dependence of piezoresistive gauge factor (GF), from 6 to 70, of poly-C films on film resistivities and grain sizes was investigated in detail. Two seeding methods, with high (1010 cm− 2) and low (108 cm− 2) seeding density, were used to grow poly-C films with small (0.3 μm) and large (0.8 μm) grains, respectively, on 4 inch oxidized Si wafers. Results show that higher resistivities and larger grain sizes yield higher GF. Poly-C piezoresistive position sensors, with a tested GF of 28 and potential GF of 70, were fabricated and integrated into a Si-based cochlear implant probe for the first time.