Charge Transport Mechanism in Atomic Layer Deposited Oxygen‐Deficient TaOx Films

Abstract

TaOx is a promising candidate for random access memory formation. To provide the possibility of 3D integration, it is grown by the atomic layer deposition (ALD). Herein, such properties of the pristine TaOx grown by radical‐enhanced ALD (REALD) as oxygen vacancies concentration and the trap energy are evaluated to reveal whether it can replace more common ion‐sputtered TaOx both in filamentary and nonfilamentary resistive random access memory (ReRAM) stacks. For this purpose, charge transport mechanism in the TiN/TaOx/Pt stacks is analyzed. It is found that charge transport through TaOx is described by the phonon‐assisted tunneling between traps model. The thermal Wt = 0.85 eV and optical Wopt = 1.7 eV trap energies are determined. The trap concentration N = 1 × 1021 cm−3 found from transport corresponds well with the oxygen vacancy concentration, obtained by ab initio simulation of valence band X‐ray photoelectron spectrum. Derived parameters are typical for the ion‐sputtered TaOx. As a result, it can be considered to replace ion‐sputtered TaOx in the nonfilamentary bilayer stacks. Moreover, the observed properties explain the possibility to achieve electroforming‐free resistive switching in a single layer REALD grown TaOx‐based stack in combination with extracting Ta electrode.