Volatile Resistive Memory Oxygen Vacancy Modulation

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Solution Overview

Problem

Existing resistive memory devices are non-volatile, requiring periodic refresh to maintain data integrity, which can be destructive and lacks multi-level cell capabilities.

Innovation Solution

A volatile resistive memory device using a resistive memory element with a barrier material portion and a charge-modulated resistive memory material portion, where oxygen vacancy concentration changes resistance states, allowing for non-destructive reading and periodic refreshing without altering the memory state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If non-volatile resistive memory devices are used, then data retention without power is improved, but periodic refresh operations are required which can be destructive and reduce reliability

Engineering Contradiction:
Improvedata retention timeVSAvoiddata integrity during refresh
Core Design Contradiction:
Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent changes the volatility parameter of the resistive memory device by controlling oxygen vacancy concentration in the metal oxide layer. By adjusting the oxygen vacancy concentration to a specific range, the device transitions from non-volatile to volatile behavior, enabling data retention through periodic non-destructive refresh operations rather than requiring destructive read-verify-write cycles

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention employs a volatile memory state that has limited retention time (short-living characteristic) but can be easily refreshed. The oxygen vacancy-mediated resistive state acts as a temporary storage that requires periodic refreshing, similar to traditional volatile memory, but with the advantage of non-destructive read and write operations that don't degrade the memory cell

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

2Power

If traditional resistive memory switching mechanisms are used, then resistance state changes are achieved, but high switching currents are required which increase energy consumption

Engineering Contradiction:
Improveswitching capabilityVSAvoidswitching current
Core Design Contradiction:
PowerVSUse of energy by moving object

Solution Approach 1:

The patent introduces oxygen vacancies as an intermediary mechanism for resistance switching. Instead of directly switching resistance through high current, the device uses voltage-induced oxygen vacancy migration to modulate resistance. The oxygen vacancies act as charge carriers that mediate the resistance change, enabling switching at lower currents compared to direct filamentary conduction mechanisms

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the switching mechanism from direct electrical breakdown or filament formation to oxygen vacancy concentration modulation. By controlling the concentration and distribution of oxygen vacancies in the metal oxide layer, the resistance state is changed through a chemical mechanism rather than purely electrical, reducing the required switching current

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If simple binary resistive states are used, then device structure is simplified, but multi-level cell capabilities are lost reducing storage density

Engineering Contradiction:
Improvememory state controlVSAvoidstorage density
Core Design Contradiction:
Device complexityVSProductivity

Solution Approach 1:

The patent enables multi-level cell capability by continuously modulating the oxygen vacancy concentration in the metal oxide layer. Instead of having discrete binary states, the resistance can be adjusted to multiple intermediate values by controlling the amount of oxygen vacancies, allowing a single memory cell to store multiple bits of information and increasing storage density without increasing device complexity

Inventive Principle:
Principle #35Parameter changes

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

Enables efficient data storage with non-destructive reading and refreshing, maintaining data integrity over time and supporting multi-level cell capabilities with reduced switching currents and improved endurance.

Implementation Method 1

a charge-modulated resistive memory material portion (86). The resistive memory element (180) enables volatile operation through changes in oxygen vacancy concentration in the charge-modulated resistive memory material portion (86)

Methodology Applied
Scientific EffectOxygen vacancy modulation: Electrical Resistance

Implementation Method 2

a barrier material portion (82) and a charge-modulated resistive memory material portion (86). The barrier material portion (82) may comprise a material selected from germanium and silicon-germanium

Methodology Applied
Scientific EffectSchottky barrier: Electrical Resistance

Data Source

PatentEP3420603B1Volatile memory device employing a resistive memory element
Publication Date: 2020.01.29 SANDISK TECHNOLOGIES LLC
  • EP3420603B1 patent drawingFigure 1A~1B
  • EP3420603B1 patent drawingFigure 2
  • EP3420603B1 patent drawingFigure 3

AI summary

A volatile resistive memory device includes a resistive memory element including a barrier material portion and a charge-modulated resistive memory material portion. The barrier material portion includes a material selected from germanium and a silicon-germanium alloy, and the charge-modulated resistive memory material portion includes a non-filamentary, electrically conductive metal oxide. The resistive memory device may be a volatile eDRAM device. In operation, reading a resistance state of the resistive memory element does not disturb the resistance state of the charge-modulated resistive memory material portion.