Analysis of Random Telegraph Noise after Soft Breakdown in the Gate Induced Drain Leakage Current

Abstract

A Random Telegraph Noise (RTN) in leakage current has been important for discovering the cause of Variable Retention Time (VRT) in Dynamic Random Access Memory (DRAM) cell transistor. Among the several leakage currents, random telegraph noise in Gate Induced Drain Leakage (GIDL) current of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is believed as the dominant cause of the VRT. Furthermore, the Soft Breakdown (SBD) has long been one of the main issues of the reliability of MOS transistor when the gate oxide layer is thinner than 4-5 nm. After the SBD occurs, the leakage current suddenly jumps without obvious indication of steps as the stress continues. If the gate tunneling current gradually increases to a certain point, then it will become high enough to cease the circuit to function. There have been many analyses about RTN in gate current after SBD, whereas there is few about RTN in GIDL current. Therefore, there is a need to study RTN in GIDL current after SBD. In this paper, Intrinsic two-level RTN in Gate Induced Drain Leakage (GIDL) RTN in GIDL current after the Soft BreakDown (SBD) by Constant Voltage Stress (CVS) in the gate-drain overlapped region was measured. In order to conduct comparative analysis, we extracted fundamental parameters of the trap, including the time constant, the trap location (xT) and the energy level (ECox-ET), the capture cross section (σc) from the measured RTN. After the first SBD, as the stress is continually given, multi-level GIDL RTN was also observed. As a result, we could predict the gate oxide degradation due to the SBD by observing the GIDL RTN after SBD.