Catastrophic latchup in CMOS analog-to-digital converters

Heavy-ion latchup is investigated for analog-to-digital converters. Differences in cross section for various ions show that charge is collected at depths beyond 50 /spl mu/m, causing the cross section to be underestimated unless long-range ions are used. Current distributions, thermal imaging, and diagnostic tests with a pulsed laser were used to identify latchup-sensitive regions. Latchup in one of the circuit types was catastrophic, even when the power was turned off within 2 ms of a latchup event. Examination of damaged devices with a scanning electron microscope showed that the failures occurred in metallization and contact regions. Current density for failure agrees with pulsed current metallization stress data in the literature.