Integration of multi-microelectrode and interface circuits by silicon planar and three-dimensional fabrication technology

Abstract

A multi-microelectrode for simultaneous recording of single-unit action potentials is a useful device for studying the organization and function of neural systems. We have fabricated a silicon probe which integrates a multi-microelectrode and interface circuits (preamplifier and analog switches) on a silicon chip by silicon planar and three-dimensional fabrication technology. This electrode has the following advantages: (1) it is easy to arrange the location of recording sites simply by changing photomasks; (2) crosstalk between the multi-electrodes can be reduced by the shielding effect of the silicon substrate; (3) integration of microelectrodes and preamplifiers on the same silicon chip eliminates the undesirable effects of stray lead capacitance; (4) analog swithces serve as selectors or multiplexers for a parallel to series conversion of multichannel signals of neural activities. In this paper, the design and fabrication processes of multi-microelectrode and interface circuits are described. In particular, the characteristics of polysilicon electrodes, design of a low-noise MOSFET for the preamplifier and silicon three-dimensional processes for the electrode probe are considered.