Using X-ray radiation to erase information from a CMOS programmable read-only memory

We have investigated the possibility of the use of X-rays to erase CMOS programmable digital ICs. In the experiment, microcontroller IC Z86 (Zilog) and 87C196KR (Intel) chips, were used. The repetitive pulsed electron accelerator URT-0.5 was used as an X-ray generator. It produced 7.6 Gy per minute (50 pps) at 5 cm from the anode on the axis, where the chips were placed. The maximum dose rate was 6.36 kGy/sec. The absorbed dose was measured using LiF-detectors. Tested chips with special program in their memory were irradiated until the information had been erased. A periodic control of the chip memory during the irradiation was performed. It has been found experimentally that CMOS PROM become free after irradiation with a dose of about 380 Gy, if it was wrapped up with 10-/spl mu/m thick Al foil. The foil only connected chip pins. It is possible to make this erasure procedure with the same chip more than twice. Irradiation erased chips were successfully tested in the working device.