Design and Fabrication of Micro Multi-Probe Electrode Arrays

This work presents a novel method of fabricating multi-probe electrode arrays on lightly doped single-crystal silicon. Such arrays are essential tools for electrical stimulation and recording of neural signals. The novel micro fabrication process, based on silicon-on-insulator (SOI) technology, inherently has good controllable probe thickness. The probe shafts were formed by doubled-sided ICP etching with the buried SiO₂ layer acting as an etch stop. The probes are 3 mm long and 100mum wide. Here the thickness of the probe (25mum) was defined by thickness of device layer on the SOI wafer. The manufacture of multi-probe with a 16-site recording electrode arrays, and Au conductor were formed on top of the probes by e-beam evaporation. SEM pictures showed sharply defined probes and tips. The neuron probe structure is mechanically strong, which can be proved by penetrating it into tofu pudding and egg without failure. The electrical yield and function were verified in impedance measurements in AMES. The magnitude of the electrode impedance was in the range of 2.46 MOmega at 1 KHz, which is consistent with neuron-physiological recordings. Besides, the magnitude of impedance inversing ratio to uncovered electrode area, were discussed at the end.