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can an UV-PROM die?

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0db:
hi, there is a dude telling me that he has just thrown a UV-PROM into the recycle bin because he is unable to read it. The PROM has been installed on an electronic board for years and perfectly working when recently checked.

Then the board moved from a laboratory to his house, and now he says "I trashed it because died", but one thing is if the content gets somehow corrupted (UV exposure? during a sunny day? because it kept the board on the desk near to a window?), one thing is the electronic inside the PROM can suddenly and unjustifiably die.

Personally, I do find hard to believe the second one.

What do you think?

greenpossum:
Of course they can die. It's a semiconductor device and so subject to those failures. Plus the trapped electrons can leak out with time. I have tossed out quite a few UV EPROMs that I could not fully erase, or after erasure, I could not program.

Gyro:
There are typically three forms of death.

The first is charge leakage (which also eventually affects Flash), where the 'programmed' charge one the floating mosfet gates leaks away over the years. This causes 0 bits to slowly (going through intermittent) transition to 1s. As long as you have an image of the flash code, it is normally possible to re-write the same UVeprom and achieve pretty much the original life again.

The second type is 'Sunburn' This used to be a common problem in labs where people set the UV lamp timer too long - particularly in labs with shared erasers where thoughtless people would put their eproms in and reset the timer without taking other peoples' out. This results in bits stuck at 1, and impossible to program to 0 again.

The third type is bits stuck at 0 after erasing particularly after several cycles of use. Sometimes curable by extending the erase time on well-used eproms for a few more cycles,  until you eventually lose them to the effects of 'sunburn.

Obviously types two and three are destined for the bin. Type one is reversible (as long as you've remembered to capture an image in good time).


P.S. It's important that the window is covered, preferably with a UV blocking Aluminium label for maximum life (I'm talking decades).

P.P.S In terms of your specific question. Leaving an eprom in a sunny window, especially in a sunny place like Zambia, might cause erasure over a week or two, however if the sun is shining through glass, then that would block the needed UV-C wavelength. I suppose it is possible that operation in strong light could cause excessive on-die leakage currents, but probably not to the extent of self-destruct. A few people actually had some success using UV-eproms as primitive imaging chips in the past. If the eprom had any sort of label on the window, this is pretty unlikely.

TomS_:

--- Quote from: 0db on April 03, 2020, 02:01:44 pm ---(UV exposure? during a sunny day? because it kept the board on the desk near to a window?)

--- End quote ---
It is my understanding that sunlight doesnt contain (enough of?) the required wavelength to erase a UV EPROM - at least not within any "reasonable" period of time. I dont think one sunny day would do it.

But I suppose its not necessarily a guarantee that some sunlight couldnt affect one. Although.. I personally have EPROMs that, as a kid some 20+ years ago), I left on the window sil for some time (maybe a couple of weeks) thinking they would be erased, but I can still read legible contents from these days (text strings etc). Whether there is any corruption to binary contents I wouldnt know unless I attempted to disassemble them.

MadTux:
Very interesting.
Never heard of the "Sunburn" failure mode before. What is the failure mode behind that?

The only "it''s dead Jim" failure mode I was aware until now, is hot carrier injection, if the EPROM is writen/erased a lot of times and electrons tunnel into the gate oxide. But then the bit will probably be stuck in programmed/0 state, instead of erased/1, as in "sunburn" failure mode. Probably the #3 failure mode, you described?

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