Some question about Backside Illumination technology...

[Celestial Traveler]

Hello everyone, I have some questions about Backside Illumination :

(1)How can BSI cause color mixture and defective pixels ?

(2)I also heard BSI has nearly 100 times dark current than FSI. What's the reason ?

(3)Since BSI is behind RGB filter array, why does QE of blue ray got degraded much more than the other 2 colors ?

(4)Why can BSI solve color shift when mounting RF wide angle lens ?

Thanks a lot.

Data Source :

(1)About color mixture and defective pixels : http://www.sony.net/SonyInfo/News/Press/200806/08-069E/

"However, compared to conventional front-illuminated structures, back-illuminated structures commonly causes problems such as noise, dark current, defective pixels and color mixture that lead to image degradation and also cause a decrease in the signal-to-noise ratio."

(2)About dark current : http://www.google.com.ar/patents/US8338856

"A typical BSI CMOS image sensor has dark current levels that are over 100 times greater than that of a front side illuminated sensor. This may be caused by the fabrication process to produce the relatively thin substrate layer of the BSI CMOS image sensor."

(3)About blue ray QE : https://www.google.com.tw/url?sa=t&...nrTnjoJL_FQB6yJnQ&sig2=eUyGBz_A3o88EclYqC2LwQ

"... resulting in decreased blue QE and increased crosstalk."

 

[Eric Fossum]

Hello everyone, I have some questions about Backside Illumination :

(1)How can BSI cause color mixture and defective pixels ?

(2)I also heard BSI has nearly 100 times dark current than FSI. What's the reason ?

(3)Since BSI is behind RGB filter array, why does QE of blue ray got degraded much more than the other 2 colors ?

(4)Why can BSI solve color shift when mounting RF wide angle lens ?

Thanks a lot.

Data Source :

(1)About color mixture and defective pixels : http://www.sony.net/SonyInfo/News/Press/200806/08-069E/

"However, compared to conventional front-illuminated structures, back-illuminated structures commonly causes problems such as noise, dark current, defective pixels and color mixture that lead to image degradation and also cause a decrease in the signal-to-noise ratio."

(2)About dark current : http://www.google.com.ar/patents/US8338856

"A typical BSI CMOS image sensor has dark current levels that are over 100 times greater than that of a front side illuminated sensor. This may be caused by the fabrication process to produce the relatively thin substrate layer of the BSI CMOS image sensor."

(3)About blue ray QE : https://www.google.com.tw/url?sa=t&...nrTnjoJL_FQB6yJnQ&sig2=eUyGBz_A3o88EclYqC2LwQ

"... resulting in decreased blue QE and increased crosstalk."

(1) I think you would get a different story from Sony in 2015 compared to 2008. Besides, even if we were back in 2008 I would disagree. This was written just to promote Sony's BSI improvements so their writer had to make it sound like BSI was crap before Sony came along.

(2) Just untrue, at least these days. In our recent experimental devices we have measured dark signal at about 10 pA/cm^2 at 60C, which is probably close to, if not a world record. They are BSI. (That is, less than 0.1e-/sec at RT with a 1.4 um pixel).

(3) In Aptina's white paper, (now ON-Semi) they did not yet have a BSI process and were trying to argue that FSI was good enough. They have since switched to BSI I think. Again, marketing materials are not technical materials. Anyway, QE is generally better across all wavelengths up to mid-red with BSI, and worse at wavelengths longer than red due to the thinness of the BSI absorption layer.

 

[Celestial Traveler]

Thanks for your answer.