TaOx Layer in ReRAM for Low-Current Switching

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Solution Overview

Problem

Resistive random access memory (ReRAM) devices face challenges in reducing current consumption for switching operations, requiring a resistive switching film that can operate at several-μA levels to improve data retention and endurance characteristics.

Innovation Solution

A resistive random access memory device configuration featuring a substrate with intersecting wiring lines, a storage cell comprising a resistive switching film sandwiched between a tantalum oxide (TaOx) layer and electrodes, where the TaOx layer is crucial for enabling low-current switching operations, with specific composition ratios and thicknesses optimizing the switching performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a conventional resistive switching film is used, then the device structure is simple, but the switching current is too high causing excessive current consumption

Engineering Contradiction:

Improvecurrent consumptionVSAvoidswitching operation reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs a composite structure consisting of a resistive switching film (such as hafnium oxide) combined with a tantalum oxide layer. This composite material system enables the resistive element to achieve reliable switching operation at several-μA-level currents, thereby reducing current consumption while maintaining switching reliability. The tantalum oxide layer specifically facilitates low-current switching by modifying the electrical characteristics at the interface with the resistive switching film.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the switching current is reduced to several-μA levels, then current consumption decreases, but data retention and endurance characteristics deteriorate

Engineering Contradiction:

Improvecurrent consumptionVSAvoiddata retention and endurance

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The composite structure of resistive switching film and tantalum oxide layer works synergistically to maintain data retention and endurance characteristics even at reduced switching currents. The specific composition ratios and thicknesses of these layers are optimized to ensure stable resistive states and reliable data storage capability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes critical parameters including the thickness of the resistive switching film (e.g., 5-50 nm), the composition ratio of tantalum oxide (TaOx with specific oxygen content), and the interface characteristics between layers. These parameter optimizations enable the device to achieve both low switching current (several-μA level) and maintained data retention/endurance performance.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If a tantalum oxide layer is added to enable low-current switching, then current consumption reduces, but device structure becomes more complex

Engineering Contradiction:

Improvecurrent consumptionVSAvoidstorage cell structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The tantalum oxide layer serves as an intermediary layer positioned between the resistive switching film and the electrode. This intermediate layer mediates the electrical interaction, enabling low-current switching operations by facilitating charge transport and modifying the electric field distribution at the interface, thereby reducing the overall switching current requirement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The integrated composite structure of resistive switching film and tantalum oxide layer is designed as a unified system where the combined functionality achieves low-current switching. The manufacturing process integrates both layers in a coordinated manner, optimizing the interface characteristics to enable several-μA-level switching while managing the structural complexity through systematic design.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The described configuration allows for low-current switching operations, enhancing data retention and endurance characteristics of the resistance change storage cell, thereby improving the overall performance of the ReRAM device.

Implementation Method 1

a resistive switching film capable of a switching operation even with a several-μA-level current

Methodology Applied

Scientific EffectResistive switching: Electrical Resistance

Data Source

PatentUS9559300B2Resistive random access memory device and manufacturing method thereof

Publication Date: 2017.01.31 KIOXIA CORP

AI summary

In accordance with an embodiment, a resistive random access memory device includes a substrate, first and second wiring lines, and a storage cell. The first and second wiring lines are disposed on the substrate so as to intersect each other. The storage cell is disposed between the first and second wiring lines at the intersection of the first and second wiring lines and includes a first electrode, a resistive switching film on the first electrode, a second electrode on the resistive switching film, and a tantalum oxide (TaOx) layer. The first electrode is electrically connected to the first wiring line. The second electrode is electrically connected to the second wiring line. The tantalum oxide (TaOx) layer is disposed between the first electrode and the resistive switching film and is in contact with the resistive switching film.