Impact of gate-to-contact spacing on ESD performance of salicided deep submicron NMOS transistors

Electrostatic discharge (ESD) failure threshold of NMOS transistors is known to degrade with the use of silicided diffusions owing to insufficient ballast resistance, making them susceptible to current localization, which leads to early ESD failure. In general, the gate-to-contact spacing of salicided devices is known to have little impact on their ESD strength. However, experimental results presented in this paper show that the ESD strength depends on the gate-to-contact spacing independent of the silicided process. Subsequently, a detailed investigation of the influence of gate-to-source and gate-to-drain contact spacings is carried out for a salicided 0.13-μm technology which provides new insight into the behavior of deep submicron ESD protection devices. It is shown that the reduction in current localization and increase in the power dissipating volume with increase in the gate-to-contact spacings are the primary causes of this improvement, which implies that even for silicided processes, the gate-to-contact spacing should be carefully engineered for efficient and robust ESD protection designs.