Characterization of Quanta Image Sensor Pump-Gate Jots With Deep Sub-Electron Read Noise

Ultra Low Noise CMOS Image Sensors

“…It shows that a 90% accuracy requires a read noise below 0.4 e − rms for single photo-electron detection and 0.3 e − rms for photo-electron count. Recently reported works are today closer than ever to these limits [9,89,90]. Here after, the possibility of performing sub-0.3 e − rms by taking advantage of the technology downscaling is discussed.…”

“…Indeed, in [10], the overlap capacitances were reduced by using reset, transfer and gates without low doped drains. In a recently reported work, a mean noise of 0.29 e − rms was measured on a small array of pixels (12 × 12), by using a low doped PN junction isolated from the transfer gate as well as a tapered SF [89]. This result came at the cost of a low full well capacity and a relatively higher lag.…”

“…C P = 0.4 f F corresponds to the case of transfer and reset gates without low doped drains and a sense node without channel stop underneath [88]. C P = 0.25 f F corresponds to the case of more advanced process refinements as [88] [89]. The numbers in labels correspond to the minimum width and optimum length as discussed in 5.…”

“…The combination of these techniques led to a C P reduction of about 47%. In [89], the capacitance C P has been reduced by using an idea called "virtual phase" well known in CCDs consisting in creating a potential profile that isolates the floating diffusion from the transfer gate. In this way, the overlap capacitance between the transfer gate and the floating diffusion (denoted C Tov in Fig.…”

“…The read noise has also been dramatically reduced to reach deep sub-electron levels [10,89,9]. Hence, CIS technologies have progressed enough now to eventually envisage photon counting.…”