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Canon Patent Application: Stacked image sensors
In this patent application, Canon is attempting to patent a stacked image sensor with improved reduction of external noise from the pads that are in between the sensor and the electronic / processing layers.
A solid-state imaging device according to the present invention comprises a first semiconductor substrate including a photoelectric conversion element, and a second semiconductor substrate including at least a part of a peripheral circuit. The peripheral circuit is for generating a signal based on the charge of the photoelectric conversion element and is arranged in a main face thereof. A main face of the first semiconductor substrate and the main face of the second semiconductor substrate are opposed to each other with sandwiching a wiring structure therebetween. The solid-state imaging device comprises a pad to be connected to an external terminal, and a protection circuit electrically connected to the pad and to the peripheral circuit. The protection circuit is arranged in the main face of the second semiconductor substrate. By thus arranging the protection circuit on the second substrate, it is possible to mitigate incorporation of external noise from the external terminal and to protect a circuit on a succeeding stage. Further, it is possible to suppress the incorporation of the external noise from the external terminal into the photoelectric conversion element.
As with other stacked sensor patents that we've seen from Canon, they are extremely detailed on the method of manufacturing and the cross-section description of the stacked sensor. In case you are wondering, a stacked sensor for most cases is also a BSI sensor. So you end up getting both sensor improvements in one generational leap in sensor technology.
Canon has been working on stacked sensors, since the early 2010's but for now, it's been purely academic. It's hard to imagine Canon making the leap all at once to stacked sensors, but anything is possible. It could very well be that they just don't see the benefit of going BSI without making the jump to stacked at the same time. Further complicating this is that the original patent in which Canon is basing this on is from a company called Magnachip Semiconductor Co., Ltd. It's certainly possible with Canon's resources, that they have licensed the IP, especially considering it's not from one of the big sensor manufacturers.
There are no guarantees that this will ever make it into a Canon camera, however, with increased pressure from Sony's sensor manufacturing which is simply turning out some incredible sensors, they have to do something significant.
US Patent Application 20190252458
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