A scaled electronically configurable CMOS multichannel intracortical recording array.
Ji, Jin
1990
Abstract
Understanding interactions among nerve cells and the structures and signal transmission properties of the central nervous system (CNS) is of great value to many scientific disciplines. The most important technique for studying the nervous system, used for the past several decades, involves recording the extracellular biopotentials generated electrochemically within individual nerve cells. The recording tools for these CNS studies have evolved from sharpened metal wire microelectrodes to thin-film multielectrode arrays to micromachined silicon thin-film arrays with integrated on-chip signal processing for reducing the susceptibility to externally-induced noise and the number of interconnection leads required. The most advanced of these active recording arrays is described in this thesis. The active recording array which was the subject of this research features precise control of probe dimensions, reduced probe shank width, 32 recording sites, and electronic site selection (of eight among the 32). On-chip circuitry also provides per-channel signal amplification, multiplexing and buffering, and use of a single data lead both for signal output and for supplying input site selection data. A total of only three leads is required for the probe, which uses a single 5 V power supply and low-power CMOS technology. Major aspects of the probe development are discussed, including limitations on probe scaling, design of the signal processing system, development of the CMOS process, and characterization of the realized probe. The scaling study shows that probe shanks as narrow as 20 $\mu$m can be fabricated using deep boron diffusion/boron etch-stop techniques. The scaled shanks are strong, and while signal crosstalk between leads on the shank increases rapidly with reduced dimensions, it remains at a low level for most structures of interest. Using the site selector, many different site configurations can be obtained electronically, including depth scanning and field zooming. The amplifier design employs a novel diode-capacitor low-pass filter to reduce the effects of recording site DC potential variations and amplifier offsets. An on-chip I/O circuit controls the single data lead for both input and output. The on-chip circuitry is fully testable using a built-in test scheme. The fabrication process merges a standard 3-$\mu$m p-well double-ploy CMOS process with silicon micromachining techniques and produces precisely controlled probe dimensions and high performance CMOS circuitry on the same substrate. The probe has been fabricated, and test results have shown that all the on-chip circuit blocks work as designed. As the result of this research, neural signals have been recorded for the first time using probes with on-chip signal processing.Other Identifiers
(UMI)AAI9034448
Subjects
Engineering, Biomedical Engineering, Electronics and Electrical
Types
Thesis
Metadata
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