Toward 1Gfps: Evolution of ultra-high-speed image sensors -ISIS, BSI, multi-collection gates, and 3D-stacking-

Evolution of ultra-high-speed image sensors is reviewed. Currently, the highest frame rate achieved by a solid-state image sensor is 16.7 Mfps, while the target of this project is 1 Gfps. To achieve this target, we propose an image sensing unit consisting of CCD pixels and a CMOS driver circuit, whereas the pixel has multiple collection gates, and the driver comprises a ring oscillator with XNOR circuits. The sensor and the driver are mounted on different IC chips by 3D stacking. Simulations confirm that the proposed technology achieves the target. In ultra-high-speed imaging, sensitivity is crucial. A technique to achieve very high sensitivity is also proposed.