A Fabrication of a Needle-Shaped Implantable Microelectrode Array for Neural Recording Using HF-HNO₃-CH₃COOH Solution

Many kinds of microelectrodes for recording have been fabricated using MEMS technology. It is difficult, however, for conventional microelectrodes to record the signals of closely spaced neurons. In addition, the tip of any implantable microelectrode must be sharp so that it only touches a single neuron. In this paper, we focus on the fabrication of needle-shaped implantable microelectrode array for the neural recording. We use a HF-HNO₃-CH₃COOH solution for isotropically wet etching of silicon to fabricate implantable microelectrodes in which the tip of the implantable microelectrodes is sharp. We show an etching time vs. diameter characteristics of the tip and bottom using a HF-HNO₃-CH₃COOH solution. After the wet etching, the implantable microelectrodes have a needle shape. As a result, we show the effectiveness of our microelectrode array fabrication process.