Development and evaluation of pixelated scintillator coupled X-ray CMOS image sensor

Abstract

Today, in digital X-ray radiographic imaging, CMOS (Complementary Metal-Oxide-Semiconductor) image sensors (CIS’s) are taking the place of CCDs in many applications due to low cost, low power consumption and chances to integrate. In this thesis, We designed and fabricated a CMOS integrated image sensor with 128x128 pixels and 50㎛ pitch using AMIS 0.5㎛ standard CMOS process as a small test-sample for developing X-ray image sensors. Active pixel sensors, analog signal processing blocks and a 10-bit pipe-lined Analog-to-Digital Converter (ADC) were integrated in a single chip. We also developed a data acquisition system in order to analyze the characteristics of the CIS. Finally, the monolithic X-ray CIS system was developed by coupling the pixelated scintillator with the fabricated CIS. We measured various properties to evaluate the performance of the CIS such as the linearity, the charge-to-voltage conversion gain, the dark current and the photo-response non-uniformity. For the scintillator coupled CIS, we took a measurement of the MTF so as to verify the spatial resolution of the obtained image. Additionally, the dark current of the CIS coupled with the pixelated scintillator was investigated. And we ultimately took X-ray images which are applicable for the high resolution X-ray imaging.