Toward 1 Gfps: A multi-collection-gate BSI imager

A concept on an ultra-high-speed image sensor is presented, targeting 1Gfps. The structure of the sensor is simple. The sensor is a backside illuminated one with the pixels, each of which is equipped with nine collection gates on the front side. During one frame interval, one collection gate collects all signal electrons generated by incident photons to the backside of the pixel. No signal electron migrates into other collection gates, prevented by a potential barrier of a p-well. Therefore, the fill factor is 100%. The collection process is repeated by changing the collection gates. Therefore, the theoretical maximum frame rate is the inverse of the travel time of an electron from the backside to a collection gate. A simulation result shows that 80% of electrons are collected within 1ns, suggesting that 1Gfps is achievable in the near future. Therefore, the sensor captures nine consecutive frames at the ultra-high frame rate.