Latchup in CMOS from single particles

Single-particle latchup in bulk CMOS was examined using heavy ions, a californium fission source, and a pulsed laser. Experiments with the laser demonstrated that latchup triggering was caused by secondary photocurrent in either the vertical or lateral parasitic transistor. Charge diffusion is shown to be important for bipolar transistor responses in latchup, which in turn makes it important to have uniform charge deposition for depths of 10 mu m or more. Californium sources have insufficient range, which causes cross sections measured with californium to be much lower than cross sections from heavy ion experiments.>