ATMEGA328 running code but with excessive power usage

[xani]

So I might've or might've not put 12V on input pit of atmega for few seconds, and now chip itself is taking around 70mA (i've buzzed all IO pins to ground and power lines so it doesn't seem to be just a short) while having basically nothing connected to output pins.

But otherwise it is running normally, code is executing and outputs send the correct data (it was a controller board for my ARM cluster). I assume chip is busted (as even with correct output it would probably cook itself in few minutes but I'm curious what exactly could fail inside the chip to cause that partial failure ?

[ataradov]

Most likely ESD diodes, or something else in I/O ring.

[danadak]

Typically, ESD causes more than one-third of the field failures in the semiconductor industry. ESD-induced failures in semiconductors can be seen in the form of leakage, short, burnout, contact damage, gate oxide rupture, and resistor-metal interface damage. CMOS scaling reduces power and increases speed, but smaller size increases susceptibility to damage of the thin gate oxide due to EOS/ESD conditions.

The shrinking size of semiconductor chips, thin gate oxides, multiple power supplies, chip complexity, and high-speed circuit operation all contribute significantly to ESD sensitivity. Shrinking gate oxide thickness needs less voltage to be damaged.

Regards, Dana.