Effect of OFF-State Stress on Gate-Induced Drain Leakage by Interface Traps in Buried-Gate FETs

The gate-induced drain leakage (GIDL) current is one of the major leakage sources in a dynamic random-access memory (DRAM) cell transistor. In addition to band-to-band tunneling (BTBT), which causes GIDL in the gate-to-drain overlap region, the generation of interface traps in the gate dielectric increases the GIDL current by trap-assisted two-step tunneling (TATT). In this article, the influence of OFF-state stress on the generation of the interface traps, which deteriorates GIDL, was quantitatively analyzed with charge pumping (CP) characterization method in buried-channel array transistors (BCATs) for DRAM cells. The applied stress increased the GIDL current while simultaneously degrading device performance including such as transconductance (g_m) and ON-state current (I_ON), due to the generation of the interface traps. By using the CP characterization, the interface traps were spatially profiled along the gate-to-drain overlap region in the junction. Trap distribution inside the energy bandgap was also characterized.