Latch-up characterization in standard and twin-tub test structures by electrical measurements, 2-D simulations and IR microscopy

The influence of different layout parameters on latchup susceptibility was studied on standard four-stripes test structures fabricated using two bulk processes: standard n-well and a twin-tub technology. Twin-tub structures show increased latchup hardness and guard-ring effectiveness, mainly due to the increased doping level and the consequent decrease in substrate and well resistances. Standard and twin-tub structures show marked three-dimensional effects in the holding characteristics, which lead to an uneven distribution of the latchup current within test structures and hysteresis in the I-V characteristics.