Unipolar resistive switching behavior in Al₂O₃/HfO₂ multilayer dielectric stacks: fabrication, characterization and simulation

Abstract

In this work, the impact of different HfO2/Al2O3-based multilayer dielectric stack (DS) configurations on the electrical characteristics and on the resistive switching (RS) performance of Ni/Insulator/Silicon devices has been systematically investigated. Significant differences are observed in the electrical characteristics of the fabricated bilayer, trilayer and pentalayer stacks compared to a single HfO2 layer of the same physical thickness. The RS analysis has shown similar low resistance state currents and set voltages for all the DS combinations whereas currents at the high resistance state and reset voltages depend on the DS. The shift of the reset voltage to lower values for HfO2 and Al2O3/HfO2/Al2O3 cases is explained by the results from thermal simulations that reveal that these differences could be associated to the different temperature distributions at the narrowest part of the conductive filament immediately before the thermally triggered reset process occurs.

On the Thermal Models for Resistive Random Access Memory Circuit Simulation

“…If all the different device material layers are included (dielectric, possibly a multilayer stack, electrodes, etc. ), the thermal conductivity, the density and specific heat of the different materials have to be considered [ 29 , 76 , 77 ].…”

“…The internal resistance calculation is performed assuming fully formed metallic-like conductive filaments of different shapes. In addition to the current calculation, we solve the 3D HE [ 29 ]. In the SD we have included the dielectric stack and part of the electrodes; precisely, 10 nm of the Si-n + (bottom electrode) and Ni (top electrode).…”

“…The conductive filament shapes employed are shown for the different cases under study, they are assumed to be metallic-like, formed by Ni atom clusters [ 24 , 55 , 80 ]. The physical parameters are the same employed in the simulation in [ 29 ].…”

“…In this respect, in the memory realm, it is important to highlight that DRAM and NAND Flash technologies will continue to hold their ground and even advance despite the slowing of Moore’s Law in the short-medium term. Although a great number of papers have been published so far on modeling and simulation issues [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ], there are many open questions that need to be addressed to improve RRAM position in the EDA context. One of the pressing modeling questions is connected with the device inherent stochasticity that produces cycle-to-cycle variability [ 19 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ].…”

Multi-Level Analog Resistive Switching Characteristics in Tri-Layer HfO2/Al2O3/HfO2 Based Memristor on ITO Electrode

“…A similar phenomenon has been indicated by Lui et al, where multilevel conductance was modulated by V Reset-stop in Al 2 O 3 /HfO 2 /Al 2 O 3 RRAM structure [ 21 ]. In the case of unipolar resistive switching, an important finding was explained by Maestro-Izquierdo et al, where 3D simulation suggests that during the RESET process, temperature distributions are different in multilayer structures [ 22 ]. Abrupt switching took place due to conductive filament (CF) narrowing in the HfO 2 middle layer due to lower thermal conductivity of HfO 2 (1.0 W m −1 K −1 ) compared to Al 2 O 3 (2.86 W m −1 K −1 ) [ 23 ].…”