IC技術を用いた神経インパルス多チャネル同時誘導用マルチ微小電極の試作

抄録

This paper describes a new multielectrode probe structure which is produced on the basis of IC techniques. A tungsten (W) electrode lead array is defined on an insulated silicon supporting carrier and is insulated from the surrounding tissue fluid by Si₃N₄ film formed by chemical vapor deposition. W is chosen from the viewpoint of durability in high temperature process of Si₃N₄ deposition. A small and mechanically strong silicon carrier having clearly shaped outline and gradual taper is produced by a combination of anisotropic and isotropic etchings. The recording area of a microprobe is formed by vacuum evaporation of gold used as the base for platinum plating for lowering the electrode impedance. Output wires are soldered onto the copper contact pads. The probe tips are 30 μm wide for a single electrode and 90 μm for a 4-channel multielectrode.
Electrode impedance characteristics of the thin film W, Au and platinum-plated electrodes are nearly the same as the conventional metal microelectrodes having the same recording areas. Calculation of the parasitic capacitances associated with the probe structure makes prediction of signal attenuation and interelectrode crosstalk possible. This microprobe has about 7% signal amplitude loss and about 1% crosstalk.
Photo-induced noise arising from the photovoltaic effect is successfully diminished to a negligible value by insulating silicon carriers from the electrolyte with thermally grown SiO₂.
The microprobes are competent for recording simultaneously from a single cell and cell groups in the brain of a cat.