Sony Unveils Manufacturing Process of DRAM-Embedded Image Sensor

Nikkeibp wrote an article about the DRAM that Sony embedded in their sensor to make cameras like the Sony a9 possible and advancements necessary to make it happen are interesting. I was going to take the time to make bullet points of it, but Image-sensors-world beat me to it with a very concise list of the most important things:

The processing flow is:

The pixel, DRAM and logic wafers are manufactured using 90nm, 30nm and 40nm processes, respectively.
The DRAM wafer and the logic wafer are joined together, and the thickness of the DRAM wafer is reduced to 3μm
The DRAM and logic wafers are electrically connected with TSVs
The stacked wafers of the DRAM and logic are joined to the pixel wafer
The 3-layer wafer stack is thinned down to 130um and connected with TSVs

The numbers of TSVs connecting the pixel layer with DRAM is ~15,000 and DRAM with logic layer is ~20,000. Both of the TSVs have a diameter of 2.5μm and a pitch of 6.3μm. The 1/2.3-inch sensor has a resolution of 21.3MP and pixel size of 1.22um.

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