Fabrication Of A Hybrid Quasi-three-dimension Neural Probe Array

The neural probe is not only an important tool for systema nervosum research, but also a useful means for the brain and the external world communicating with each other. It plays a great role in many ways such as the neural signal detection, the recovery of nerve function and the realization of brain-computer interface. Inspired by the Utah probe, the structure and the fabrication process of a hybrid quasi-three-dimensional neural probe array were reported in this thesis. The aim is to fabricate the probe arrays directly on the readout circuit chip fabricated by the standard CMOS process, thus to realize the integration of the probe arrays and the readout circuit. The work around thesis includes:(1) According to the fabrication process reported in this thesis, a silicon-based structure of the probe arrays, which was improved in the details on the basis of the Utah probe, was provided. And the layout of the corresponding process was given also.(2)The process for the structure transfer and the idea about "milling" in mechanical process were introduced in the fabrication. By means of flip chip and multi-blade mixing dicing techniques, it made the shaping of the probe arrays on the readout circuit chip directly. Then it used the metal electrode deposition process and insulation layer process to fabricate the probe arrays further. The probe arrays achieved finally, was a 10×10 scale three-dimension arrays with centre-to-centre separation of 400 μm. In the probe arrays, whose good rate was more than 95%, the width of a single probe was 100 μm, the tip angle was 25°, and the height was more than 1.4 mm.(3)It performed the function test for the hybrid neural probe both in the normal saline and on Sprague Dawley rat in vivo. And the result showed that the probe was able to obtain the corresponding nerve signal.There are two innovative points in the fabrication process reported in this thesis:First, it used the hybrid process to realize the interconnection between the probe arrays and the readout circuit chip. It flipped chip for face-down bonding first, and shaped the probe arrays later, what did not made the probe arrays avoiding difficulties of the transfer after the shaping only, but also simplified the interface between the probe arrays and the readout circuit effectively. And then it made larger scale probe array possible.Second, it used a combination of different shapes blades dicing, with the particular cutting programme, to finish the shaping of silicon needle array greatly. Even the good rate of the silicon needle after dicing ran up to 100%. These two made no any high-temperature process and silicon wet etching process, which would damage the circuit, included in the entire fabrication process compatible with the CMOS process.As the hybrid quasi-three-dimension neural probe array was fabricated successfully, the purpose for the thesis was achieved. With the result of the function test, it proved that the neural probe could basically meet the requirements of biological experiments. In the future work, there would be a lot of improvements in many aspects such as the structure of the probe, the process, the correlative material, and the testing work what would make the neural probe greater potential in competition.