PROCESS TECHNOLOGY OF MULTIELECTRODE MICROPROBE FOR A MINIMALLY INVASIVE NEUROCOMPUTER INTERFACE
Abstract
The work is devoted to the development of technology of manufacturing a multielectrode microprobe
(neuroprobe) using surface micromachining and anisotropic wet etching of silicon based
on the infrastructure of the Research and Education Centre "Nanotechnologies" of Southern Federal
University. The development was carried out to implement a typical design of the neuroprobe, which
consists of a base, several beams of rectangular shape with a pointed end and electrical interface.
The process flow based on 4 photolithography steps and includes 18 main operations like substrate
cleaning, thermal oxidation, plasma-chemical deposition of silicon oxide an nitride d, rapid thermal
annealing, plasma-chemical etching of silicon nitride and oxide, isotropic and anisotropic wet etching
of silicon oxide and monocrystalline silicon, and metals deposition by electron-beam evaporation.
Experimental researches of anisotropic wet etching of monocrystalline silicon in a potassium
hydroxide solution through a mask of plasma deposited silicon oxide, as well as the effect of rapid
thermal annealing on the mask resistance were conducted. The effect of the solution concentration
(from 10 to 40%) on the etching rate and surface roughness at 80 °C was studiedThe etching in 27–
30 % KOH solution leads to formation of a surface with a minimum average roughness value of 13
nm. The etching rates of monocrystalline silicon and silicon oxide were 1.5 μm/min for (100) face,
3 nm/min for (111) face, and 10 nm/min, respectively. Rapid thermal annealing at 600 °C for 3 min
increases resistance of silicon oxide the alkaline solution by 2 times. The developed technology was
tested on the example of formation a two beam neuroprobes on 420 thick 4’’ silicon wafer (100). A
series neuroprobe structures was fabricated. The developed technology could be used for the fabrication
of neuroprobes with various numbers and placement of beams and electrodes.
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