Analysis of a new ESD failure and its improvement

The increased leakage of off-state MOSFETs after an electrostatic discharge (ESD) event was studied for output transistors with thin gate oxide and lightly doped drain (LDD) structures. A new type of leakage increase called a soft breakdown was found at relatively low ESD testing voltages. This soft breakdown is caused by the creation of interface traps due to snap-back stressing during the ESD event. The creation of interface traps enhances the interface-trap-to-band tunneling current at the drain side of the MOSFETs. It was also shown experimentally that an additional arsenic implantation into the n/sup -/ region increases the human body model (HBM) ESD threshold to more than 2000 V.<>