Image Sensors World blogs about the Canon high ISO sensor design.

Image-sensors-world discovered and discuss an older canon whitepaper detailing the challenges of large 19um pixels in their ME20F-SH camera.

Canon whitepaper "Advances in CMOS Image Sensors and Associated Processing" by Shin Kikuchi, Daisuke Kobayashi, Hitoshi Yasuda, Hajime Ueno, and Laurence Thorpe, first presented at the Hollywood Professional Alliance (HPA) Tech Retreat in Palm Springs on February 19, 2016 talks about challenges in 19um large pixel design (note a strange definition of conversion gain, probably meant to be image lag):

The image sensor design sought optimization of three key attributes of the photosite:
1. Sensitivity – determined by the quantum efficiency of the photosite
2. Saturated charge quantity (sometimes termed full well capacity) – that determines dynamic range
3. Efficiency of the charge transfer (sometimes termed conversion gain) – the goal being to transfer all electrons during each reset period to ensure full sensitivity

Canon says it was able to achieve 70% QE at 500nm in monochrome sensor.

It's amazing that Canon continues to use the 500nm design rules with a high degree of success.
Get the whitepaper here:

http://learn.usa.canon.com/app/pdfs/white_papers/White_Paper_AdvancesinCMOS.pdf