A 32-site neural recording probe fabricated by double-sided deep reactive ion etching of Silicon-on-Insulator substrates

A neural probe with a 32-site electrode array was fabricated using an all-dry Si etch based micromachining process. The fork-like probe shafts were formed by double-sided deep reactive ion etching (DRIE) of a silicon-on-insulator (SOI) substrate, with the buried SiO2 layer acting as an etch stop. The shafts typically had the dimensions 5 mm x 25 μm x 20 μm and a tip taper of 4°. An array of Ir electrodes, each 100 μm, and Au conductor traces were formed by e-beam evaporation. SEM studies showed sharply defined probes and probe tips. The function was verified in bench-top measurements in saline. The magnitude of the electrode impedance was in the 1 MΩ-range @ 1 kHz, which is consistent with neural recordings.