Extended Data Fig. 1: The integrated CMOS/Photonics platform.
From: Neuropixels Opto: combining high-resolution electrophysiology and optogenetics
a. Cross-section of the probe shank obtained with a scanning electron microscope (SEM) showing the monolithically integrated platform combining the CMOS platform (for electrical recording) and SixNy-based photonics (for optical stimulation). Left labels: layers used for the recording sites and readout IC, based on the 130-nm SOI CMOS Aluminum back-end-of-line process (Al BEOL) that was developed for the Neuropixels 1.0 probe. They point to the 130-nm CMOS layer (bottom), the 6 Aluminum metal layers (middle) and the Titanium nitride electrode (top). Right labels: the photonic modules that were added between the M6 metal layer of the CMOS BEOL and the recording electrode to enable optical stimulation. The photonics also use the M6 metal layer for controlling the photonic switches that are used to select the optical emitter. b. Schematic of the probe build-up, illustrating the photonic modules that were added to the CMOS platform, which include: grating couplers handling the light coupling from a fiber to the chip; an underlying reflector layer (metallic mirror); a SixNy photonic waveguide module; a full TiN/Al/TiN light blocking layer that is only interrupted for the VIA and bond pads, to protect the CMOS circuits from laser light scattered by the photonic waveguides; a heater module to make thermo-optical switches; a stress compensation layer to cancel the stress induced by the extra photonics layers, keeping the shank tip deflection within the spec of ±200 μm; and a deeper VIA etch to contact the heaters and electrodes.
