High resolution large formatted CMOS FLAT PANEL SENSORS for X-ray

Abstract

This paper describes world largest monolithic CMOS flat panel sensor (FPS) and high speed amplifier with columnar CsI scintillator directly deposited onto the active area. These elements have been employed as a compact digital camera module for dynamic X-ray imaging will be used in digital mammography and scientific image measurement. The FPS has a diagonal size of 11 inches and 4, 416 × 3,520 pixel array (15,544,320 pixels), which features a high resolution of 10 lp/mm with single pixel drive. The key material of the FPS is monocrystalline silicon optimized for use in digital radiography. The sensor utilizes a direct deposited scintillator layer made from high resolution, high luminance CsI crystals grown into a needle structure onto a large formatted photodiode array for indirect detection of X-ray images. The CsI scintillation spectrum well matches the spectral response range of the photodiode. The CsI has the advantages of high sensitivity and high resolution compared to GOS phosphors screen. These image sensors are manufactured in a 0.15μm 12 inches CMOS process allowing a high fill factor of 76% for 50μm pixel. Only one chip is taken from one 12 inches wafer in order to realize a seamless active area. The monolithic amplifier blocks have 4,416 channels of charge amplifiers with internal CDS (Correlated Double Sampling) circuit has an optimal design yielding a high gain of 0.26 μV per electron and a data transfer speed of 17.8 Mbytes per second in sufficient low noise. This paper discusses the system design, dynamic range, resolution, detective quantum efficiency (DQE) and imaging performance using ACR mammography phantom.