A 0.27e-rms Read Noise 220-μV/e-Conversion Gain Reset-Gate-Less CMOS Image Sensor With 0.11-μm CIS Process

A low temporal read noise and high conversion gain reset-gate-less CMOS image sensor (CIS) has been developed and demonstrated for the first time at photoelectron-counting-level imaging. To achieve a high pixel conversion gain without fine or special processes, the proposed pixel has two unique structures: 1) coupling capacitance between the transfer gate and floating diffusion (FD) and 2) coupling capacitance between the reset gate and FD, for removing parasitic capacitances around the FD node. As a result, a CIS with the proposed pixels is able to achieve a high pixel conversion gain of $220~\mu \text{V}/\text{e}^{ {{-}}}$ and a low read noise of 0.27e $^{-}_{\text {rms}}$ using correlated multiple-sampling-based readout circuitry.