Sony Develops a Stacked CMOS Image Sensor Technology

Sony announced that it has succeed in developing Pregius S, a stacked CMOS image sensor technology. It employs Sony's proprietary global shutter function with back-illuminated pixel structure to deliver both distortion-free, high imaging performance and miniaturization. The new technology is intended for industrial equipment used in fields such as manufacturing, inspection, and logistics.

Conventional CMOS image sensors equipped with global shutter function temporarily store charge signals in the memory area located next to the photodiode to resolve image distortion (focal plane distortion) caused by the time shift due to the row-by-row readout. In front-illuminated CMOS image sensors, there is a wiring layer on the silicon substrate forming the photodiode, and with such a structure, the benefit is that it is easy to form a light shield for protecting the charge signal temporarily stored in the memory area from leaked light. For this reason, conventional CMOS image sensors with global shutter function have adopted a front-illuminated pixel structure. However, the wiring on top of the photodiode hinders the incident light, which creates an issue when attempting to miniaturize the pixels.

In response to this, Sony has developed a proprietary pixel structure that achieves the global shutter function on a back-illuminated structure that has superior sensitivity characteristics, thereby resolving the issue of miniaturization. Normally, when pixels are miniaturized, the sensitivity and saturation characteristics deteriorate, but the new technology enables a reduction in pixel size to 2.74 μm while maintaining performance of those characteristic, thereby achieving about 1.7 times higher resolution than conventional front-illuminated CMOS image sensors. This makes it possible to measure and inspect objects in a wider area and with higher accuracy in manufacturing, inspection, logistics and other applications.

Going forward, Sony will work to develop products equipped with this stacked CMOS image sensor employing its proprietary global shutter function with back-illuminated pixel structure for various industrial applications and intelligent transportation systems, including development of derivatives for signal processing circuits to be mounted. The company plans to start shipping sample units during the summer or later this year.