Studies of the critical LDD area for HCI improvement

Hot carriers, the high kinetic energy carriers due to high electric field in the channel region, are injected into the gate oxide and form interface states, which in turns causes degradation of MOS device performance. The hot carrier effect has become more severe as the device size continues to scale down to submicron range. This aging phenomenon that threatens the circuit and product lifetimes warrants it to be considered as the key challenge in reliability. The most widely used device structure for improving the hot carrier reliability is the lightly doped drain (LDD). Studies on LDD engineering have been carried out for deep submicron technology to enhance device hot carrier immunity. The result shows 10 times improvement in hot carrier injection (HCI) DC lifetime from LDD implant optimization. This substantial improvement is attributed to the mechanisms of reduction and departure of high electrical field from the drain area.