Sony comes out with the industry's first 3-layer stacked CMOS image sensor with DRAM for smartphones. The new image sensor consists of a DRAM layer added to the conventional 2-layer stacked CMOS image sensor with a layer of back-illuminated structure pixels and a chip affixed with mounted circuits for signal processing.
This newly developed sensor with DRAM delivers fast data readout speeds, making it possible to capture still images of fast-moving subjects with minimal focal plane distortion as well as super slow motion movies at up to 1,000 frames per second (approximately 8x faster than conventional products in full HD (1920x1080 pixels).
In order to realize the high-speed readout, the circuit used to convert the analog video signal from pixels to a digital signal has been doubled from a 2-tier construction to a 4-tier construction in order to improve processing ability.
Although there are speed limitations in the interface specifications for outputting signals from image sensors to other LSIs, this sensor uses DRAM to store signals read at high speed temporarily, enabling data to be output at an optimal speed for the standard specifications.
As a result, the product is capable of reading one still image of 19.3 million pixels in only 1/120 of a second (approximately 4x faster than conventional products*3), thereby supporting high-speed image capture.
The newly developed sensor also includes solutions for the various technical problems inherent in the design, for instance, reducing the noise generated between the circuits on each of the three layers. Sony has made the most of the expertise in stacked image sensor manufacturing technology, which it pioneered and developed over the years, to ensure that quality and reliability remains high despite the complex three-layered construction.