Planer Multi Electrode Array Coupled CMOS Image Sensor for in vitro Electrophysiology Arata Nakajima 1,3 , Toshihiko Noda 1,3 , Kiyotaka Sasagawa 1,3 , Takashi Tokuda 1,3 ,Yasuyuki Ishikawa 2,3 , Sadao Shiosaka 2,3 and Jun Ohta 1,3 1 Graduate School of Materials Science, 2 Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan Phone: +81-743-72-6051 E-mail: ohta@ms.naist.jp 3 JST-CREST, 4-1-8 Honcho, Kawaguchi, Saitama 331-0012, Japan 1. Introduction In neuroscience, little is known about the dynamics of micro-circuitry in brain regions such as cerebral cortex and hippocampus. To elucidate those mechanisms, sever- al techniques have been developed such as fluorescent imaging, multi-electrode array (MEA) systems and so on[1, 2]. Since MEA probe is transparent and compatible with optical microscopy, combination of those two greatly enhances the visibility of the circuit dynamics with mo- lecular and electrophysiological tools. However, optical systems tend to be large-sized and costly equipments, which minimize the benefit of multimodal recordings by prohibiting large scale monitoring or downsizing the possible recording points. To solve those problems, we propose a multi-functional recording device for in vitro electrophysiology and de- signed Multi-electrode Array Coupled CMOS image (MARC) sensor. The novel recording device was designed based on Complementary Metal Oxide Semiconductor (CMOS) image sensor, and micro electrode arrays were fabricated using the top-metal layer of analog Large Scale Integrated circuits (LSI) platform. In this paper, we re- port design of MARC sensor and fabrication of Pt black microelectrode on Al metal layer in our MEA system. We also report a preliminary result from functional valida- tions by imaging mouse brain slice. 2. Multi-electrode Array Coupled CMOS Image Sensor Concept Fig. 1. shows schematic representation of Multi elec- trode Array Coupled CMOS image (MARC) sensor. This sensor chip was designed for the simultaneous data ac- quisition from biological samples by using electrical re- cording/stimulation and fluorescence/transmitted light imaging. To implement such functions, the sensor has photodiode (PD) array, preamplifier, read-out scanner, and microelectrode array. The electrode array was fabri- cated on the same plane with PD array, so that both light and ionic current can be obtained on the same contact surface with biological samples. The surface of the sensor chip is chemically modified with biocompatible material. Design of MARC sensor Fig. 2 shows microscopic image of MARC sensor. The inset shows magnified single microelectrode. Table 1. shows specification of the sensor chip. The sensor was fabricated on 2-poly 4-metal, 0.35 m standard CMOS process. The effective recording field on MARC sensor is 1.4 mm x 1.4 mm, which has 180 x 180 pixels. The pixel array is composed of 7.5 m x 7.5 m, 3-transistor Active Pixel Sensors (APSs). For the electrical interface with biological substrate, 8 x 8 microelectrode array was fa- bricated using the top metal wiring layer of Al. As shown in Fig. 2, the microelectrode has two dimensional lattice structures. The square shaped hole among lattice is light receptive field of photodiode. The layout of top metal layer assigned for the electrode is overlapped with underlying shied layer of APS. In this way, multi electrode array is nicely woven into pixel array without drastically chang- ing the fill factor of a single pixel. This layout design po- tentially enables simultaneous electrical recording or stimulation and imaging at the same recording sites. 2.2 mm Electrode Pixel(3x3) 60 m 22.5 m 2.1 mm Electrode and Pixel Array 1.4 mm Fig. 1. Schematic representation of Multi-electrode Array Coupled CMOS image sensor (MARC sensor) for in vitro electrophysiology. Fig. 2. Microscopic image of MARC sensor, magnified images of single electrode and 3 x 3 pixel array. Multi-electrode array and pixel array were fabricated on the same plane on the sensor chip. -1170- Extended Abstracts of the 2010 International Conference on Solid State Devices and Materials, Tokyo, 2010, pp1170-1171 G-8-2