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Lecture 21: Image Sensors (63)

In FSI, silicon is placed below the diode. Why is silicon placed above the diode in BSI? If light needs to pass through the silicon before hitting the diode, wouldn't this decrease quantum efficiency?


I'm also curious about that - I was wondering what exactly the role of silicon is in the sensor. I recall that for BSI, the silicon must be shaved really thin, which is maybe why it doesn't decrease quantum efficiency too much. But would making it really thin detract from whatever else it is supposed to do, or is it okay because it's a semiconductor?


I would also be curious to know the specific trade offs in that regard. We can see the benefits in these slides but if this were the better way unilaterally, why wasn't it always BSI instead of FSI?


Agree with the point above, I was also curious as to why FSI a thing in the first place, I was thinking it might have been a lot easier to manufacture than BSI. On Quora, I found this link ( and it from this it appears that the reason FSI remains popular and is used is because SONY (which supplies a lot of parts to camera manufacturers) makes FSI parts.

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