Impact of ESD-induced soft drain junction damage on CMOS product lifetime

The impact of ESD-induced soft drain junction damage on product lifetime was investigated. Several thousand input-output (I/O) pads of a 0.35 μm CMOS IC were stressed by ESD (electrostatic discharge) and subsequently subjected to bakes, ESD re-stress and high temperature operating life tests. While the ESD-induced soft drain junction damage appears to be stable versus temperature stress and ESD re-stress, it results in early failures during accelerated operating life tests. These life test failures are caused by breakdown of the gate oxide which was left unbroken during the ESD stress that caused the ESD-induced soft drain junction damage. Thus, ESD-induced soft drain junction damage might cause a reliability risk (latent ESD failure). Consequently, it needs to be avoided by assuring sufficient robustness of the IC against this ESD damage mechanism. A leakage current criterion of 1 μA is rather large to detect this kind of damage after ESD stress