Surprised no one has mentioned yield. With larger chip size, getting good yield becomes a challenge, especially with smaller nodes. 28nm is an extremely mature node with 8+ years of prod volume (in excess of 3k wafer starts a week in multiple fabs).
The physical size of the sensor is locked because it is tied to entire families of camera, lens, etc sizes that are very difficult to change. So that is the given constraint, and the other parameters flow from it.
It's not that they really want this size/node. It just is the optimization of what they are allowed to work within.
You can still keep the physical sensor size the same but use a smaller process. Of course, if you can use 450mm+ wafer sizes at 25nm vs. 300mm wafers at <=10nm then suddenly it's a massive price difference.
But you still need to have the same wafer area if you are keeping the same sensor size. So you can't have 300mm wafers at <10nm, you still need 864+mm (for a FF sensor).
Surprised no one has mentioned yield. With larger chip size, getting good yield becomes a challenge, especially with smaller nodes. 28nm is an extremely mature node with 8+ years of prod volume (in excess of 3k wafer starts a week in multiple fabs).
Ding ding ding!
The physical size of the sensor is locked because it is tied to entire families of camera, lens, etc sizes that are very difficult to change. So that is the given constraint, and the other parameters flow from it.
It's not that they really want this size/node. It just is the optimization of what they are allowed to work within.
You can still keep the physical sensor size the same but use a smaller process. Of course, if you can use 450mm+ wafer sizes at 25nm vs. 300mm wafers at <=10nm then suddenly it's a massive price difference.
But you still need to have the same wafer area if you are keeping the same sensor size. So you can't have 300mm wafers at <10nm, you still need 864+mm (for a FF sensor).
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