TDDB Mechanism in a-Si/TiO₂ Nonfilamentary RRAM Device

Abstract

Mechanisms of time-dependent-dielectric-breakdown (TDDB) in non-filamentary a-Si/TiO2 RRAM cell (a-VMCO) have been examined in this work, including defects generation in the grain boundary, defects clustering and different defects generation rates in a-Si and TiO2 layers. The unique feature of a bimodal Weibull distribution at low resistance state (LRS) and a single shallow slope distribution at high resistance state (HRS) cannot be explained by the above mechanisms. By using a combination of constant-voltage-stress (CVS), time-to-breakdown Weibull distribution and random-telegraph-noise (RTN) based defect profiling in devices of various sizes, layer thickness and processes, it is revealed that the defect profile is modulated when switching between HRS and LRS and the correlation of defect profile modulation with local defect generation rate can explain the difference in Weibull distributions at HRS and LRS. The transition from bimodal distribution at LRS to a single-steepslope with thinner a-Si layer, and the good area scaling of Weibull distribution at HRS but not at LRS, can also be explained. The critical layers affecting the TDDB in a-VMCO are identified, providing useful guidance for device performance improvement.

Investigation of Time Dependent Dielectric Breakdown (TDDB) of Hf0.5Zr0.5O2-Based Ferroelectrics Under Both Forward and Reverse Stress Conditions

“…Interestingly, forward breakdown follows classical Weibull distribution, while reverse breakdown shows non-linear behavior (square points) indicating its deviation from the classical Weibull distribution (dash lines). Such phenomenon has been reported in dual-layer high-k dielectrics in logic transistors [14]. However, this cannot explain our case since there is only one insulating layer in our MIM capacitor structure.…”

Short-Term Memory Dynamics of TiN/Ti/TiO2/SiOx/Si Resistive Random Access Memory

“…The gradual conductance modulation in the TiO 2 -based RRAM system can be explained by the nonfilamentary switching model [ 39 , 40 , 45 , 46 , 47 ]. Resistive switching in the interface-type model occurs by barrier modulation at the interface between the electrode and insulator rather than by the rapid conductance change caused by the formation and rupture of local filaments [ 39 , 40 , 45 , 46 , 47 ]. Strong oxygen vacancies can be created at the interface between Ti and TiO 2 because Ti is highly reactive to oxygen [ 45 , 46 ].…”

In Quest of Nonfilamentary Switching: A Synergistic Approach of Dual Nanostructure Engineering to Improve the Variability and Reliability of Resistive Random‐Access‐Memory Devices

“…Analog incremental current in S4 devices is also beneficial for neuromorphic type applications as compare to the abrupt current change in S2 devices. [ 2,16,25 ]…”

“…[ 13–15 ] In another approach, a nonfilamentary switching is beneficial to improve the stability of the resistance states. [ 16,17 ] As reported by researchers, nonfilamentary switching has some unique features like nonlinear current–voltage ( I – V ) with self‐compliance nature, low switching current, gradually increasing conductance, area scalability, and so on. Geometrically, nonfilamentary devices constructed with a V o scavenger and a barrier layer controlling the current through the stack.…”