The Quanta Image Sensor (QIS) has been proposed as a possible next-generation image sensor. In the single-bit QIS, the specialized, sub-diffraction-limit sized binary-output photo-element sensitive to a single photoelectron is called a “jot”. Central to single-bit as well as multi-bit QIS implementations is single-electron sensitivity (˜0.15 e-r.m.s.) which can be obtained from high, in-pixel conversion gain, e.g., more than 1000 μV/e-. For the high conversion gain needed, the capacitance of the floating diffusion (FD) node needs to be minimized. According to the present inventors' previous QIS work, the capacitance of the FD node has been greatly reduced, but further reductions in FD node capacitance and/or additional or alternative ways to reduce FD node capacitance may still be advantageous and/or desired. By way of example, in some QIS pixel designs the reset gate (RG) overlap capacitance may still contribute about 10% of the total FD capacitance, so further reduction of this RG overlap capacitance may be possible, and may be desired or necessary for some implementations.
USPTO Backgrounds
USPTO Backgrounds