Neural recording chip with penetrating Si microprobe electrode array by selective vapor-liquid-solid growth method

This paper reports on the development of neural recording chip device with penetrating Si microprobe electrode array using IC-process. The Si microprobe electrode array each with a few microns in diameter was grown at predetermined positions with interconnection-wirings. Controlling the diameter and the length of Si probes can be realized by a selective vapor-liquid-solid (VLS) growth. In this work, Si probes with 2 μm in diameter and 60 μ in length were fabricated, which were conductive-Si probes and they were encapsulated with SiO₂ layers. To reduce the impedance of Si probes, the tips of Si probes were coated with a metal Au layer. As a result, penetrating Si microprobes measured in saline solution, showed impedance of the order of 300 k to 500 kω at 1 kHz. Packaging techniques for the probe chip were performed with a fluid-tight chamber and a flexible-printed-circuit of polyimide for neural recording experiments.