CMOS-based neural probe with enhanced electronic depth control

This paper reports on the design, fabrication, and testing of complementary-metal-oxide-semiconductor (CMOS)-based high-density neural probes. An enhanced electronic depth control (EDC) scheme is implemented using a switch matrix integrated in the slender probe shaft, allowing simultaneous reconfiguration and recording on unaffected channels. The number of simultaneously available analog output channels is increased to 16 compared to the initial EDC probes of our group. Probe shaft length up to 10 mm with a shaft width and thickness of 100 µm and 40 µm, respectively, have been realized. A maximum number of 334 electrodes is achieved on the longest probe variant with an inter-electrode spacing of 30 µm along the probe shafts. The addressing and switching scheme is realized using the commercial 0.18 µm six-metal, double-poly CMOS process from XFAB combined with an in-house post processing of the electrode metallization and probe patterning. The probe functionality is verified using bench tests and the electrode impedance characterization revealing 1.4±0.2 MΩ at 1 kHz for platinum electrodes with a diameter of 30 µm.