Correlation between digital differential voltage contrast and infrared microscopy analysis of latch-up in CMOS

Results of latch-up analysis obtained by scanning electron microscopy voltage contrast and infrared (IR) microscopy are correlated and discussed. Voltage contrast detects surface potential changes due to latch-up firing, while IR microscopy reveals recombination radiation emitted by silicon (Si) regions where current density is maximum. Voltage contrast analysis may be difficult in very large-scale integrated (VLSI) circuits because well and substrate regions can be masked by overlying conductors. On the contrary, thanks to the transparency of Si to IR radiation, IR microscopy can detect latch-up by observing the reverse of the device and is not limited by a high metal density.