All in all, this looks like a good candidate for deprocessing. I hope not to lose this sample like the others, as it's the only one I have at this moment.

Related, there is one more mystery here, which concerns the damage done to the metal layers of this die. Here I can clearly see the intact metal3 in the power distribution routing in the bottom left corner of the snippet, which is bright yellow like elsewhere on the die. This then transitions to green, the abrupt transition typically means the metal there was etched away by something -- probably the remains of whatever I used to decap this. Going up further though, I see green turning into pale yellow colour, very similar to metal2. The other snippet also shows a similar story, with metal3 being removed leaving some green residue, which is also removed afterwards leaving transparent oxide with some junk inside.

I would so, so much like to know a) what is this green lining? some kind of nitride? and b) what reaction caused it to be stripped. This could be so much useful in deprocessing.

@joost_rekveld Thank you for your kind words!

The vast majority of the images taken do not involve any deprocessing steps like polishing or lapping, which is why oftentimes all the interesting bits are obscured by upper layers. If the device only has one metal layer, I can deprocess it using chemical means. I started experimenting with mechanical deprocessing recently, you can find a thread on this in my account if you are interested to see how the results look.

There is not much more to it than a) removing the die from the package b) cleaning it up and mounting on a slide c) running the imaging in an automated fashion and d) post-processing the collected tile images into a single panorama image of the whole die. I guess there is also step e) posting about it here. :-) Some imaging runs may go on for more than a day if the sample is particularly large.