A Silicon Carbide 256 Pixel UV Image Sensor Array Operating at 400 °C

Abstract

An image sensor based on wide band gap silicon carbide (SiC) has the merits of high temperature operation and ultraviolet (UV) detection. To realize a SiC-based image sensor the challenge of opto-electronic on-chip integration of SiC photodetectors and digital electronic circuits must be addressed. Here, we demonstrate a novel SiC image sensor based on our in-house bipolar technology. The sensing part has 256 (16×16) pixels. The digital circuit part for row and column selection contains two 4-to-16 decoders and one 8-bit counter. The digital circuits are designed in transistor-transistor logic (TTL). The entire circuit has 1959 transistors. It is the first demonstration of SiC opto-electronic on-chip integration. The function of the image sensor up to 400 • C has been verified by taking photos of the spatial patterns masked from UV light. The image sensor would play a significant role in UV photography, which has important applications in astronomy, clinics, combustion detection and art. INDEX TERMS Silicon carbide (SiC), image sensor, ultraviolet (UV), photodiode, high temperature, bipolar junction transistor (BJT), transistor-transistor logic (TTL).

Integrated 64 pixel UV image sensor and readout in a silicon carbide CMOS technology

“…This brings the total readout time down to 2.6 s, or 0.39 Hz, which is a 13 times improvement to the synchronous clock. As a fair comparison to the reported 256 pixel array in a SiC BJT technology 15 the timing scheme is extrapolated, resulting in a total time for 256 pixels of 8.4 s, which is an improvement of 15 times.…”

“…Extensive research effort was made on silicon carbide photodetectors, as they make excellent visual-blind UV detectors. Over the years the technology has come a long way, leading for example to a UV-index monitoring demonstrator board 14 and UV imager 15 . Reliability studies on the aging effects show promising results, revealing little to no change in the device performance 16 – 18 .…”

“…Fraunhofer IISB already demonstrated UV photodetectors 26 – 28 , that allow integration with the CMOS fabrication technology. However, at present the only previously reported optoelectronic system in SiC, was achieved in the BJT technology at the KTH in Sweden by Hou et al 15 . This system includes 256 addressable pixels, 1959 transistors, and runs at 8.25 W and 7.7 mHz.…”

SPICE Modeling and Circuit Demonstration of a SiC Power IC Technology

“…Shakir et al demonstrated a SiC 555 timer and a SiC comparator that are operational under 500°C [14] with an in-house SiC bipolar junction transistor (BJT) process [15]. Hou et al reported a 16x16 SiC UV image sensor array operating at 400°C with the same BJT technology [16]. Research groups from NASA and Ohio Aerospace Institute [17] have also demonstrated SiC JFET digital ICs that operate across a wide range of temperatures (−190°C to 812°C).…”

Hybrid Pixels With Si Photodiode and 4H-SiC MOSFETs Using Direct Heterogeneous Bonding Toward Radiation Hardened CMOS Image Sensors

“…Operation of 4H-SiC bipolar junction transistors (BJTs), junction field effect transistors (JFETs), and metal-oxide-semiconductor transistors (MOSFETs) have been demonstrated in high temperature environments [4][5][6][7][8][9][10][11][12][13][14]. In terms of the image sensor, 4H-SiC has already demonstrated operation as a UV imaging system with 256 pixels at 400°C [15]. However, 4H-SiC does not have sufficient absorbance at visible light [16].…”