RRAM Resistance Switching Layer Voltage Sequencing

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Solution Overview

Problem

Resistive random-access memory (RRAM) devices face issues with yield and efficiency due to instability in resistance-switching layers, leading to high reset current variability and data retention errors after baking, which affects the reliability and distinguishability of storage data.

Innovation Solution

A method involving the formation of a resistance-switching layer between electrodes, with specific voltage applications to adjust resistance states, including a forming voltage, initial reset voltage, set voltage, and second reset voltage, followed by a weak set voltage operation and baking to stabilize the memory device's electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a resistance-switching layer is formed and subjected to standard forming and reset operations, then the basic memory function is achieved, but reset current variability increases and data retention reliability deteriorates after baking

Engineering Contradiction:
Improvedata retention reliabilityVSAvoidreset current variability
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

A weak set voltage is applied to the resistance-switching layer before the baking process to preliminarily adjust and stabilize the resistance distribution. This preliminary action ensures that when the device undergoes baking, the reset current variability is minimized and data retention reliability is maintained, preventing the deterioration that would otherwise occur with standard operations alone

Inventive Principle:
Principle #10Preliminary action

2Stability of the object's composition

If multiple voltage operations are applied to adjust resistance states, then electrical characteristics are stabilized, but the process complexity increases

Engineering Contradiction:
Improveelectrical characteristics stabilityVSAvoidvoltage operation process complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

A weak set voltage with specific parameters (lower magnitude than standard set voltage, applied for a predetermined time period) is introduced to adjust the resistance distribution in the resistance-switching layer. This parameter change approach stabilizes electrical characteristics by controlling oxygen vacancy distribution, achieving reliable data retention without requiring complex multi-step voltage sequences

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

The method improves the stability and reliability of RRAM devices by reducing reset current variability and maintaining low reset currents, enhancing data retention and distinguishability post-baking, thereby improving the overall yield and performance of the memory devices.

Implementation Method 1

applying a forming voltage to the resistance-switching layer such that the resistance of the resistance-switching layer is decreased

Methodology Applied
Scientific EffectElectrical stress-induced resistance change: Electrical Resistance

Implementation Method 2

applying an initial reset voltage to the first electrode or the second electrode layer such that the resistance of the resistance-switching layer is increased

Methodology Applied
Scientific EffectElectrical stress-induced resistance change: Electrical Resistance

Implementation Method 3

baking the memory device layer after the second set voltage is applied to the first electrode or the second electrode

Methodology Applied
Scientific EffectThermal annealing: Annealing

Data Source

PatentEP2930760B1Method for forming memory device
Publication Date: 2018.02.07 WINBOND ELECTRONICS CORP
  • EP2930760B1 patent drawingFigure 1A
  • EP2930760B1 patent drawingFigure 1B
  • EP2930760B1 patent drawingFigure 2A~2B

AI summary

A method includes forming a resistance-switching layer (104) and a second electrode (106) over a first electrode (102). The method includes applying a forming voltage to the resistance-switching layer such that the resistance of the resistance-switching layer is decreased. The method includes applying an initial reset voltage to the first electrode or the second electrode such that the resistance of the resistance-switching layer is increased. The method includes applying a first set voltage to the first electrode or the second electrode such that the resistance of the resistance-switching layer is decreased. The method includes applying a second reset voltage to first electrode or the second electrode such that the resistance of the resistance-switching layer is increased. The method includes applying a second set voltage to first electrode or the second electrode such that the resistance of the resistance-switching layer is decreased. The second set voltage is lower than the first set voltage.