Nonvolatile Memory Element Oxygen Reservoir Design

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Solution Overview

Problem

Conventional nonvolatile memory elements with transition metal oxide as a variable resistance material exhibit significant variation in resistance change characteristics, which affects their reliability and performance.

Innovation Solution

A nonvolatile memory element is designed with a variable resistance layer comprising a first oxide layer with p-type carriers and a second oxide layer with n-type carriers, along with an oxygen reservoir region and a local region, where the oxygen content atomic percentage varies to control resistance change, reducing parasitic resistance and stabilizing the resistance change characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional transition metal oxide layer is used as a variable resistance layer, then the device structure remains simple, but significant variation in resistance change characteristics occurs

Engineering Contradiction:

Improveresistance change characteristicsVSAvoidvariable resistance layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The variable resistance layer is segmented into multiple oxide layers with different carrier types (p-type and n-type). This segmentation allows each layer to contribute differently to the overall resistance change mechanism, with the local region in the n-type layer dominating the resistance change characteristics while the p-type layer provides oxygen reservoir functionality, thereby reducing variation in resistance change.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a local region within the n-type oxide layer that has distinct oxygen content characteristics compared to other regions. This local region with lower oxygen content atomic percentage becomes the dominant site for resistance change, while other regions provide supporting functions. This local quality differentiation stabilizes the resistance change characteristics by concentrating the variable resistance mechanism in a specific region.

Inventive Principle:

Principle #3Local quality

2Reliability

If a single oxide layer is used, then manufacturing is easier, but parasitic resistance effects occur

Engineering Contradiction:

Improveresistance change characteristicsVSAvoidvariable resistance layer fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The variable resistance layer is divided into multiple oxide layers with different carrier types (p-type and n-type). This segmentation allows each layer to contribute differently to the overall resistance change mechanism, with the local region in the n-type layer dominating the resistance change while the p-type layer provides oxygen reservoir functionality, thereby reducing variation in resistance change.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The p-type oxide layer acts as an intermediary between the n-type oxide layer and the electrode, providing oxygen reservoir functionality that mediates the oxygen transport during resistance switching. This intermediary layer facilitates controlled oxygen exchange, reducing parasitic resistance effects while maintaining manufacturing feasibility through established multi-layer fabrication techniques.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration effectively reduces variation in resistance change characteristics, enhancing the stability and reliability of nonvolatile memory elements by dominating resistance change with the local region and avoiding parasitic resistance effects.

Implementation Method 1

recent researches have found that a likely cause of such resistance change is change in defect density of conductive filaments formed in a binary transition metal oxide by an oxidation-reduction reaction

Methodology Applied

Scientific EffectOxidation-reduction reaction: Redox Reactions

Implementation Method 2

a first oxide layer comprising a metal oxide having non-stoichiometric composition and including p-type carriers; a second oxide layer located between and in contact with the first oxide layer and the second electrode and comprising a metal oxide having non-stoichiometric composition and including n-type carriers

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS8957399B2Nonvolatile memory element and nonvolatile memory device

Publication Date: 2015.02.17 PANASONIC SEMICON SOLUTIONS CO LTD

AI summary

A variable resistance nonvolatile memory element includes a first electrode, a second electrode, and a variable resistance layer including: a first oxide layer including a metal oxide having non-stoichiometric composition and including p-type carriers; a second oxide layer located between and in contact with the first oxide layer and a second electrode and including a metal oxide having non-stoichiometric composition and including n-type carriers; an oxygen reservoir region located in the first oxide layer, having no contact with the first electrode, and having an oxygen content atomic percentage higher than that of the first oxide layer; and a local region located in the second oxide layer, having contact with the oxygen reservoir region, and having an oxygen content atomic percentage lower than that of the second oxide layer.