Multiple ion implantation profile using differential channel dose

Multiple ion implantations are frequently used, especially for extension regions in high-speed MOSFETs, to ensure symmetrical doping profiles. In the process simulation, each process step is treated independently and the final impurity concentration after the multiplied ion implantation is linearly multiplied by the number of first-implantation processes. However, as the channeling tail of the ion implantation profile is saturated in high dose regions, the simple multiplication of the profiles induces artificial deeper junction depths. To solve this problem, we introduced a differential channel dose, which enables us to generate accurate ion implantation profiles, and here we will demonstrate that the conventional treatment of the multiple ion implantations predicts worse short channel effects especially for nMOSFETs.