128 × 96 Pixel-parallel three-dimensional integrated CMOS image sensors with 16-bit A/D converters: By direct bonding with embedded Au electrodes

We demonstrate for the first time the operation of 128 × 96 pixel-parallel three-dimensional (3D) integrated CMOS image sensors with 16-bit A/D converters (ADCs). 3D integration of the photodiode (PD), pulse-frequency-modulation (PFM) ADCs and 16-bit counters were implemented within every pixel by utilizing direct bonding with embedded Au electrodes in a SiO2 insulator. We designed an in-pixel charge-transfer circuit suitable for the PFM-ADC to obtain high sensitivity. The developed sensor successfully confirmed its excellent linearity with a dynamic range of 96 dB, corresponding to a 16-bit value. We also captured 128 × 96 pixel-parallel video images constructed from the 16-bit outputs, demonstrating the feasibility of ultimate imaging devices for the next-generation.