N-FET HCI reliability improvement by nitrogen interstitialization and its mechanism

In this paper, we demonstrate a new process to improve the N-FET´s hot carrier lifetime more than 10 times, compared to that of traditional LDD formation process. It is composed of phosphorus (P₃₁) and nitrogen (N₁₄) co-implant through TEOS liner and followed by Si₃N₄ (SIN)/TEOS deposition. With this new method, the substrate current (Isub) can be reduced more than 2 times at the same drain current (Idsat). However, the quasi-static C-V measurement does not reveal the less interface state (Dit) generation during the stress for the capacitors with N₁₄ implant. Through SIMS analysis, it is found that the doping profiles of B₁₁ and P₃₁ have been modulated at the LDD region. Therefore, we consider that N₁₄ implant into the LDD region will enhance the transient enhanced diffusion (TED) effect, which leads to the Isub reduction and then improves hot carrier lifetime.