Trying to View an Active 555 with an Electron Microscope
Ben uses an electron microscope in an attempt to take a look at a 555 while it’s operating. He writes:
I used my DIY scanning electron microscope to view a 555 timer circuit while it was powered. The circuit is a simple oscillator with a very long time constant to make the changes easy to see. My plan was to view the silicon die itself, and hopefully discern changes in its internal circuitry as the oscillations occurred. As it turns out, I was only able to “see” the charge of the electrical wires going to the chip socket. There is likely a clear oxide layer that covers the silicon die, and needs to be removed with hydrofluoric acid in order to use the SEM to inspect the die itself while powered.
While he wasn’t successful this first time out, it was still pretty cool to see how he went about it, and learning the hazards of this kind of work. I look forward to seeing his next attempt!
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A scanning tunneling- or some variant of an atomic force microscope would probably be better for observing changes as the circuit operates.
KA1OS: If you have access to either of those and you’d like to make a video, we’d love to post it! 🙂
Google -voltage contrast SEM-;… this is a common failure analysis lab technique. Using a standard SEM with a test socket for the device, and a low accelerating voltage (+/- 1 kv), the charge in the circuit provides the black/white contrast as charge moves through gates and registers…. this looks really cool in digital/memory ICs. I did a stint on a VC-SEM in a FA lab back in the ’80’s as a college co-op student.