Tuesday, March 17, 2015

Sony Stacked Sensor Features Internal Transformer

Chipworks reverse engineers Sony 2nd generation stacked sensor, the 13MP, 1.12um pixel IMX214, first announced about a year ago.

The main features of this stacked BSI device when compared to the respective features on the first generation stacked CIS are:
  1. refinement and modifications to the TSVs used to connect CIS signals to the ISP circuitry
  2. simplification of the manufacturing process to enable lower cost of manufacturing
  3. moving of most of the circuitry from the CIS die to the ISP die, d) changes in pixel circuitry for SME functionality
  4. changes in the organic layer stack on the light receiving side of CIS to bring microlenses closer to the pixel cathodes.

IMX214 bottom (logic) die

But the most intriguing part of the report is a small transformer somewhere on the chip:

If vias can be an indication of the transformer size, its inductance appears to be well below 100pH. Such inductors are not very useful at frequencies below 10GHz. I wonder why does Sony need it?

Update: Chipworks says that transformer part is just a generic marketing image, not related to IMX214 circuitry. The report flyer will be modified soon and the transformer image will be removed.

Another Chipworks report covers 28.2MP Samsung DSLR BSI sensor S5KVB2XX09, featuring 3.6um pixels. The highlights of this report are:
  • Samsung is the first to market with a back-illuminated APS-C format CMOS image sensor
  • An array of partially masked pixel pairs is embedded in the active pixel array to facilitate the phase-detection AF functionality
  • A new shared-pixel architecture is employed for the active pixel array

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