A CMD-only reproducible field degradation and its reliability aspect
Simulated electrostatic discharges (ESD) according to the human body model (HBM) and the charged device model (CDM) were compared in their ability to reproduce a leakage degradation observed in the field. Only CDM successfully reproduced the electrical and the physical failure signature in the input inverter of the active circuitry. A homebuilt CDM-tester was used to degrade a significant number of input pins for a reliability or latency study. An experimental investigation of the impact of this degradation on reliability showed that the degraded devices are latently damaged. They have input leakage currents still within specification, but show a highly increased sensitivity to electrical overstress and to ESD stress according to the human body model with a 100 per cent correlation to the CDM degradation. A standard burn-in test showed that they can cause early failures. The degradation is caused by a damage in the gate oxide of an input transistor, and the latent failure is caused by a 'breakdown' of the damaged oxide. Latency was shown to appear systematically.