Three-dimensional integrated CMOS image sensors with pixel-parallel A/D converters fabricated by direct bonding of SOI layers

Abstract

We report the first demonstration of three-dimensional (3D) integrated CMOS image sensors with pixel-parallel A/D converters (ADCs). Photodiode (PD) and inverter layers were directly bonded with the damascened Au electrodes to provide each pixel with in-pixel A/D conversion. We designed ADC with a pulse frequency output and fabricated a prototype sensor with 64 pixels. The developed sensor successfully captured video images and confirmed excellent linearity with a wide dynamic range of more than 80 dB, which showed feasibility of pixel-level 3D integration for high-performance CMOS image sensors.