Investigation of self-heating induced hot-carrier-injection stress behavior in high-voltage power devices

In this paper, we investigate hot carrier injection (HCI) stress induced self-heating behavior for high-voltage n-type Lateral-Diffused-MOSFET (NLDMOS) multi-finger devices. A NMOS device with more poly fingers, for the first time, is found to suffer more threshold voltage drift (ΔV_t) but less linear current drift (ΔId_lin) under HCI stress at high gate and drain voltages. The experiment of monitoring device temperature is carried out and TCAD simulations are performed to investigate the physical mechanisms. The effect of poly gate finger numbers (PGFN) is attributed to higher lattice temperature with more PGFN, resulting in higher electrical field in the channel region and lower electrical field in the drift region. HCI behavior in ΔV_t and ΔId_lin for different PGFN devices at various ambient temperatures are verified by TCAD simulation. In addition, the effect of PGFN on AC HCI stress and DC HCI Safe-Operation-Area (SOA) are studied. All the experimental findings can be well explained by the effect of self-heating during HCI stress mode.