Hybrid Pixel Devices with SOI-Si photodiode and 4H-SiC MOSFETs for Radiation-Hardened Image Sensors

For the electronics, radiation hardness has been required especially for decommissioning of the Fukushima Daiichi nuclear power station. So far for such the decommissioning operations, many robots have been installed, however the available time for operation is limited by electronics, in particular, image sensors. At a pixel device in a conventional Si CMOS image sensor, Si MOSFETs as reset (RST), source follower (SF), row selector (RS) , are sensitive and vulnerable to radiation, rather than Si photodiodes (PD). Then a combination of Silicon carbide (SiC) MOSFETs and Si PD would be a candidate for the pixel device of the radiation-hardened CMOS image sensors. In this work, SOI (Silicon-On-Insulator)-Si PD and 4H-SiC MOSFETs were integrated in a same substrate for the radiation hardened image sensors. The typical feature size of the SOI-Si PD was 500 μm2 and that of 4H-SiC MOSFET was channel length/ width = 10 μm/ 50 μm. Under dark condition, the output voltage shift from the reset state was 0.62 V. On the other hand, under visible light of 7 klux, the output voltage shift became 0.74 V. The voltage difference between dark and visible-light illuminated condition was dependent on the reset (RST) frequency. As the RST frequency decreased from 100Hz, the voltage difference became larger. As the results, the hybrid pixel devices with SOI-Si PD and 4H-SiC MOSFETs were sucessfully demonstrated.European Conference on Silicon Carbide and Related Materials (ECSCRM 2018