A Low kTC Noise and Low FPN Reset Method for Pixel in ToF Image Sensor

In this paper, a
$256 \times 128$
rolling shutter time of flight (ToF) CMOS image sensor (CIS) with a low kTC noise and low fixed pattern noise (FPN) reset method is presented. The pixel adopting the proposed reset method has two taps and three reset transistors. The two taps enable this ToF image sensor to capture depth image quickly and the three reset transistors ensure reduction of the kTC noise and FPN. This kind of ToF image sensor is implemented in a
$0.13~\mu \text{m}$
one-poly four-metal CMOS technology. The physical size of the pixel with the proposed reset method is
$10\,\,\mu \text{m}\,\,\times 10\,\,\mu \text{m}$
with a maximum fill factor of 69%. The chip size of the sensor is
$4671\,\,\mu \text{m}\,\,\times 3406\,\,\mu \text{m}$
. Measurement results show that the proposed reset method for ToF pixel can reduce the kTC noise and FPN at room temperature effectively. The maximum reduction of kTC noise is
$394.9 ~\mu \text{V}$
. The maximum reduction of FPN is
$531.8 ~\mu \text{V}$
. Therefore, ToF sensors with the proposed reset method can achieve low thermal noise and high spatial uniformity.