This Sony stacked sensor uses an unusual design to help to save costs and boost performance

Sony has added a new sensor to its list of commercial photography semiconductors, featuring a new architecture that reduces production costs while boosting camera performance.

The Sony IMX820 is a 24.5MP partially-stacked back-illuminated (BI) CMOS sensor that features an architecture called chip on wafer (COW). This is an unusual enough design that it's the only sensor on the list described as COW-BI.

But what is COW-BI, and why does it matter? To produce COW sensors, Sony cuts silicon wafers of pixels into individual chips before bonding them with chips containing circuitry cut from another silicon wafer. Until now, sensors have typically featured an architecture called wafer on wafer (WOF), which sees a whole silicon wafer of pixels bonded to another silicon wafer containing the logic, with chips then cut.

However, this architecture runs the risk of the entire wafer becoming defective if an issue arises, a problem which the COW technique solves by cutting up the individual silicon wafers into chips beforehand.

COW architecture also brings performance benefits for cameras. The technique enables Sony to precisely stack chips with specific functionality, which can speed up data transfer and reduce energy consumption – features that are required for 8K and 120fps+ recording. Stacking chips in this way also enables Sony to incorporate dedicated AI-driven layers into sensors, which can analyze images before they are processed.

While Sony is only now sharing information on the IMX820 publicly, it may not exactly be brand new. Many major camera brands don't disclose where their sensors are sourced from, particularly when using sensors manufactured by another company. But, Sony Alpha Rumors suggests that this COW-BI design could be the sensor inside the Nikon Z6 III and Lumix S1II.

At this stage, only the IMX820 model name has been added to the list of commercial sensors on the Sony website, with the specification yet to be shared. But what’s interesting is that this newly-added model is the only one designated with a COW-BI design. There is speculation that the 33MP CMOS BI sensor featured in the Sony A7 V also has a COW architecture, but this hasn’t been confirmed by Sony.

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On other sensor fronts, Sony recently revealed that its 68MP 120fps global shutter sensor, IMX928, has been distributed to industrial clients for testing.