Pulsed Infra-Red Microscopy for Debugging Latch-Up on CMOS Products

A Near Infra Red Microscope has been used to debug latch-up problems on CMOS products. The microscope is used to image the recombination radiaton emitted by the forward biased junctions in SCR latch-up. If latchup occurrs at one location it will spread like a cancer untill several sites have latched up. This causes the traditional heat sensing techniques to give incorrect results. Techniques were developed to view and understand the mechanisms which cause latch-up spreading. Various kinds of I/O latch-up modes have been studied and described.