A Novel Method to Improve Laser Anneal Worsened Negative Bias Temperature Instability in 40-nm CMOS Technology

From the measured data, the impact of the rapid thermal process (RTP) and laser spike anneal (LSA) sequence on negative bias temperature instability (NBTI) and current gain was investigated on 40-nm complementary metal-oxide semiconductor technology. For the conventional sequence RTP/LSA, a significant threshold voltage V_T shift is observed due to the NBTI. The thermal gradient in the LSA step induces a thermomechanical stress inducing oxide fixed charges and an increase in Si dangling bonds at the SiON/Si interface, thus increasing the V_T shift. By moving the LSA step to before the RTP anneal and coimplanting a carbon atom in the source/drain extension implant processing, the obvious V_T shift could be suppressed to the same as the RTP-only anneal. Best of all, the sequence change does not impact the gain of the original combination anneal over the RTP-only anneal in the on current of devices.