A 0.88 e‾ _rms 8-Mpixel 3D-Stacked Low Temporal-Noise CMOS Image Sensor With Auto-Zero Single-Slope ADC, Fast Correlated Multi-Sampling, Row-Wise Noise Reduction, and Dark Current Non-Uniformity Calibration Techniques

This paper presents a low temporal noise, low-power, 8-Mpixel, rolling-shutter (RS)-type, back-illuminated CMOS image sensor (CIS) employing through silicon via (TSV) 3D-stack technology. To achieve temporal noise less than 1 <roman xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</roman><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>rms</i></sub><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup>, we explored auto-zero (AZ) column single-slope (SS) ADC and fast correlated multi-sampling (CMS) techniques. The pixel signal was sampled two times by the readout circuits using a 9-bits ADC, resulting in a 10-bits digital output. To enhance image quality in low light conditions, we adopted a parity column counter (PCC) for power supply stabilization and H-banding elimination, and employed row-wise noise reduction (RWNR) and dark-current non-uniformity calibration (DCNUC) techniques for reducing row-wise noise and improving image uniformity. Our CIS chip was fabricated using a 55nm 1P4M (pixel substrate) and a 55nm 1P5M (logic substrate) CIS 3D stacked process. The die area is ~3.99<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup>3.45 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with 1.008-μm pixel pitch and the total energy consumption is 170mW under a 2.8V analog-VDD and a 1.2V digital-VDD. The chip achieves a temporal noise of only ~0.88 <roman xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</roman><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>rms</i></sub><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup>, fixed pattern noise (FPN) of ~25.08μV<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>rms</roman></sub>, row-wise noise of ~5.5μV<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>rms</roman></sub> and an energy efficiency figure-of-merit (FoM) of ~0.6 <roman xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</roman><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>rms</i></sub><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup>nJ/step at a frame rate of 60 frames per second (FPS).