Anomalous Hot carrier injection induced degradation of drain current in High-Voltage NMOS with Shallow Trench Isolation

In 25V High-Voltage NMOS manufactured by 28nm High-K Metal Gate (HKMG) process, the first peak of Isub appears at Vg=6.7V. Due to the hot carrier injection (HCI, stress condition @Vg=6.7V, Vd=27.5V), the linear current Idlin (Vd=0.05V) firstly increases and then decreases with time when the gate voltage Vg is low (<4V), and Idlin monotonously decreases when Vg is high (>4V), which is different from previous research. Under a certain stress time, the degradation of drain current (Vg=25V) is the largest when Vd=4.5V. Two competing mechanisms were proposed to explain the maximum degradation at Vd=4.5V. The mechanisms above were confirmed utilizing TCAD simulation and were integrated in manufacturing process. The obtained results confirmed the presume and helped to study and improve the HCI reliability.