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Comment by Harmohit | Hacker News Reader

This is so cool! "Dissecting" a processor like this could be a fun educational activity to do in schools similar to dissecting a frog, but without the animal rights issues.

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Personally, I think everyone should try opening up a chip. It's easy (if the chip isn't in epoxy) and fun to look inside. You need a metallurgical microscope to examine the chip closely, but you can see interesting features even with the naked eye.

I didn't know there is such a thing as a metallurgical microscope. What makes them different from biological microscopes? And what is there primary purpose? I am assuming they don't make microscopes just for dissecting chips.

Biological microscopes illuminate the sample from below, as the samples are typically transparent. Metallurgical microscopes illuminate reflective samples from above.

*"Below" meaning "on the opposite side from the objective" - you illuminate _through_ the sample.

Metallurgical microscopes illuminate the sample "from the top side". The actual implementation even goes as far as making sure the illumination happens on the optical axis of the objective (as if the light was emitted from your eyes/camera, reflected from the sample and then seen by your eyes/camera). They are also called reflected light or epi-illumination microscopes.

Biological microscopes, on the other hand illuminate the sample from the back side (which doesn't work for fully opaque objects).

A regular biological microscope shines the light from below. This is good for looking at cells, but not so useful when looking at something opaque. A metallurgical microscope shines light from above, through the lens. They are used for examining metal samples, rocks, and other opaque things.

An external light works for something like an inspection microscope. But as you increase the magnification, you need something like a metallurgical microscope that focuses the light where you are looking. Otherwise, the image gets dimmer and dimmer as you zoom in.

In some places, you've shown the same part of the circuit both with and without the metal layers. How did you find the same location on the die after taking the die out of the microscope, removing the additional layers and putting it back?

I figured that I would want to study the standard-cell circuits, so I made a detailed panorama of one column of standard-cell circuits with the metal. Then after removing the metal, I made a second panorama of the same column. This made it easy to flip back and forth. (Of course, it would be nice to have a detailed panorama of the entire chip, but it would take way too long.)

Discarded RFID cards and the like provide a practically free source of minimally-encapsulated ICs, also often made on an old large process that's amenable to microscope examination.

Having looked at a few RFID cards, there are a couple of problems. First, the dies are very, very small (the size of a grain of slat) so they are hard to manipulate and easy to lose. Second, the die is glued onto the antenna with gunk that obstructs most of the die. You can burn it off or dissolve it with sulfuric acid, but I haven't had success with more pleasant solvents.

Decapping a processor produces toxic waste, which has to be disposed of. Processors, properly handled, last a lot longer than frogs, and can be re-used again and again: to a first approximation, processors do not wear out. I would expect that manufacturing a new processor causes more suffering to more frogs than is caused by killing a frog for dissection.

That said: we have video players in our pockets. Sure, dissecting one frog might be a more educational experience than watching somebody else dissect a frog, but is it more educational than watching 20 well-narrated dissections? I suspect not. I don't think we need to do either.

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