Bulk and surface degradation mode in 0.35μm technology gg-nMOS ESD protection devices

We study failure mechanisms in 0.35μm process grounded-gate nMOS electrostatic discharge (ESD) protection devices stressed by high current - ESD like - pulses. Stress evolution of leakage current and low frequency noise is correlated with the position of the ESD damage analyzed using optical beam induced current (OB1C) technique. While a kink-free-like IV characteristics and low noise magnitude are typical for a bulk damage at the drain-contact region, a kink-like IV shape and large random telegraph signal (RTS) noise accompanies surface damage under the gate oxide. The role of hot-carriers in the degradation of the Si/Si0₂ interface and gate oxide, and leakage current mechanism are discussed.