A Large-Size HfO₂ Based RRAM Structure Suitable for Integration of One RRAM with One InGaZnO Thin Film Transistor for Large-Area Applications

Abstract

This work aims at finding a HfO2-based resistive random-access memory (RRAM) structure suitable for the integration of one RRAM with one InGaZnO thin film transistor (TFT) for large-area applications such as flexible electronic circuits. One of the major concerns is that the compliance current (CC) required for the formation of stable and strong conductive filaments in the forming and set processes as well as the maximum current required in the reset process in a large-size RRAM should be lower than that of the maximum current a TFT can deliver. In this work, an ultrathin Al2O3 layer of 2 nm was inserted between the HfO2 switching layer and the reactive Ti layer of the top electrode in the RRAM with the structure of Pt (bottom electrode)/HfO2/Al2O3/Ti/TiN (top electrode). With the ultrathin Al2O3 layer, the forming voltage was greatly reduced, and the CC for stable forming and set operations and maximum reset current can reach a low current level that an InGaZnO TFT is able to provide, while the device-to-device variation of the forming operation and cycle-to-cycle resistance variations of the set and reset operations are improved significantly.

A first-principles investigation into the electronic characteristics of phase changes in ZnO at high pressures

“…In fact, a very accurate pseudo-Potential Linearized Augmented Plane Wave (PP-LAPW) approach was used, which is implemented in the Siesta code based on Density Functional Theory (DFT), to get trustworthy findings [18].Local Density Approximation (LDA) [19] and Perdew-Burke-Ernzerh of Generalized Gradient Approximation were used to tackle the exchangecorrelation effect (PBE-GGA) [20].Thus, in the current work, we have chosen two fundamental parameters: the 350 eV kinetic cutoff energy for plane waves and the 3×3×3 k-point Monkhorst-Pack mesh. This resulted in a convergence of the overall energy to less than 5×10 5 eV/atom and the maximum ionic Hellmanne Feynman force to less than 0.05 eV/Å. Additionally, we have worked to expand the k-points to 3×3×6 in order to obtain more precise answers for each of the electrical and optical aspects.…”

“…Zinc oxide, ZnO is one of the most important semiconductor, with a broad direct and estimated energy gap of 3.4 eV, with very large exciton energy estimated at60 mega volts [1][2][3][4]. Recently, scientists have concentrated on a large number of semiconductors, due to their multiple advantages at the industrial and technological level [5][6][7]. Indeed, ZnO has remarkable and diverse applications, including gas sensors, photo catalysts and thin layers related to electronic and electro-optical devices [8][9][10][11][12].Under normal conditions, the dynamically stable phase of ZnO is the four surface wurtzite (B4) phase with covalently bonded Sp3 [13].…”