RRAM Filament Formation via Stepped Voltage Pulses

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Solution Overview

Problem

The initial formation of conductive filaments in resistive random access memory (RRAM) devices is challenging due to the need for high voltage and current, which can lead to uncontrolled filament formation and device damage if not managed properly.

Innovation Solution

Applying a series of voltage pulses with increasing amplitude and duration, along with controlled current limits, to gently form filaments without excessive voltage, ensuring reliable and controlled filament formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high voltage and current are applied to form conductive filaments in RRAM devices, then filament formation is achieved, but uncontrolled filament growth and device damage occur

Engineering Contradiction:

Improvefilament formation reliabilityVSAvoiddevice damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The voltage pulse is divided into multiple discrete steps (first voltage level, second voltage level, third voltage level) rather than applying a single high voltage. This segmentation allows controlled progression through different formation stages, achieving reliable filament formation while preventing uncontrolled growth and device damage through incremental voltage increases.

Inventive Principle:

Principle #1Segmentation

2Productivity

If a single high voltage pulse is applied to form filaments, then filament formation is achieved, but the process is uncontrolled and damages the device

Engineering Contradiction:

Improvefilament formation speedVSAvoidfilament formation control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The filament formation process uses periodic voltage pulses with different amplitudes applied in sequence. Each pulse duration is configured to be equal to or greater than the relaxation time of the resistive dielectric layer, allowing the system to stabilize between pulses. This periodic action with varying amplitudes achieves both efficient filament formation and precise control, preventing the uncontrolled growth that would occur with a single high voltage pulse.

Inventive Principle:

Principle #19Periodic action

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

This method allows for reliable and controlled filament formation, improving the operational performance and reliability of RRAM devices by preventing uncontrolled filament growth and device damage.

Implementation Method 1

by applying the proper voltage across the dielectric layer, a conduction path (typically referred to as a filament) can be formed through the dielectric material layer

Methodology Applied

Scientific EffectElectrical breakdown: Avalanche Breakdown

Implementation Method 2

The voltage and current needed to form the filament are relatively high (i.e. significantly higher than the voltages needed to set and reset the memory cell)

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9959927B2Multi-step voltage for forming resistive access memory (RRAM) cell filament

Publication Date: 2018.05.01 SILICON STORAGE TECHNOLOGY INC

AI summary

A memory device and method comprising a metal oxide material disposed between and in electrical contact with first and second conductive electrodes, and a voltage source configured to apply a plurality of voltage pulses spaced apart in time across the first and second electrodes. For each one of the voltage pulses, an amplitude of the voltage increases during the voltage pulse.