Friday, August 23, 2013
Aptina Files for DTI Between Analog, Digital, Pixel Areas
Aptina's patent application US20130206962 "Imaging Systems with Backside Isolation Trenches" by Peter Rupert Barabash Barr and Aaron Kenneth Belsher proposes deep trench isolation (DTI) to cut a thin BSI layer into analog, digital, and pixel array portions:
Deep trench isolation was also shown by ST Microelectronics at the Image Sensor Workshop 2011 (Tournier).
ReplyDeleteThe ST one was between pixels in the array to improve pixel-to-pixel crosstalk. Aptina proposes DTI to isolate between analog, digital and the pixel array. Sort of obvious solution to me, but the whole patent system today seems to encourage obvious patents.
Deletewhat's the advantages of this isolation?
ReplyDeleteIt can be seen as a substitute for deep Nwell, to a degree.
DeleteFor example, many pixels need negative TG voltage for low dark current. One can fence-off the negative bootstrap area, so the Pwells there would be isolated from the rest of the chip. Alternatively, one can isolate the pixel array from the rest of the sensor, then raise its bulk voltage to 1V or so. Then 0V coming from the row address decoder would look negative with respect to the bulk of the pixel array.
There are few other nice uses too.