DESIGN OF SILICON MICROPROBE FOR MINIMALLY INVASIVE NEURAL INTERFACE

Abstract

Microprobes have become an important tool in the study of brain activity. Research and development in the field of invasive neurointerfaces is aimed at reducing the characteristic damage to the nervous tissue by reducing the diameter of the implanted probes to less than 100 μm. Such structures are produced by micromachining, in particular, by types of anisotropic etching. In this case, the size and shape of the probe are influenced by the etching conditions. The latter should betaken into account at the designing of the probe. The paper evaluates the ranges of the geometric parameters of a silicon microprobe taking into account the etching conditions and the number of electrodes. Analytical calculations were carried out for the structure of the probe, represented by four regions of different widths, carrying up to seven electrodes. The dependences of bottom base width of a trapezoidal section of the probe and the size of the mask on the thickness and width of the top base are received. The admissible ranges of sizes for the proposed case of the four-level microprobe are established; in particular, the minimum values of the width of the top base were 17, 28, 39 and 50 microns, and the corresponding ranges of permissible values of the probe thickness for cases with 1 electrode – 30–58 microns, 2 and 3 electrodes – 30–51 microns, 4 and 5 electrodes – 30–43 microns, and for the case of a probe with 6 and 7 electrodes – 30–35 microns. The correction value of the mask size is estimated, reflecting the effect of etching conditions on the probe geometry.