RRAM Filament Localization via Laser Stimulation

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Solution Overview

Problem

Current methods for determining the spatial location of conductive filaments in resistive random access memory (RRAM) devices are invasive, stressful, and time-consuming, making it difficult to gain insights into electric and material properties, especially when analyzing a statistically significant number of devices.

Innovation Solution

A method using a raster-scanned laser signal at low device bias voltage to non-invasively locate the filament, creating a map of sense signal changes to determine the 2-dimensional coordinate position of the filament, allowing for quick localization and correlation with other electrical information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If invasive methods are used to determine filament location, then measurement capability is improved, but device stress and measurement time increase

Engineering Contradiction:

Improvefilament location detectionVSAvoiddevice stress

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a laser beam as an intermediary tool to indirectly detect filament location through optical interactions rather than direct electrical probing. The laser beam interacts with the filament's electrical field or thermal properties, allowing spatial localization without physical contact or high-stress electrical signals that would damage the device

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces invasive electrical measurement methods with optical detection using a laser beam. This substitution eliminates the need for physical contact or high-current electrical probes that stress the device, using light-matter interaction instead to achieve filament localization through changes in optical properties or electrical field modulation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If invasive methods are used to determine filament location, then measurement capability is improved, but measurement time increases

Engineering Contradiction:

Improvefilament location detectionVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces time-consuming invasive electrical measurement procedures with rapid optical detection using a laser beam. The laser can quickly scan or probe the device, and optical detectors provide immediate feedback on filament location through changes in light transmission, reflection, or absorption, dramatically reducing measurement time compared to sequential electrical probing methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Difficulty of detecting and measuring

If high bias voltage is used to locate filament, then detection capability is improved, but device stress increases

Engineering Contradiction:

Improvefilament detectionVSAvoiddevice stress

Core Design Contradiction:

Difficulty of detecting and measuringVSStress or pressure

Solution Approach 1:

The patent uses a laser beam as an intermediary to detect filament location without applying high electrical stress. The laser interacts with the filament's electromagnetic field or thermal signature, allowing detection of low-resistance filaments through optical means rather than requiring high bias voltages that would stress or damage the device structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the detection parameter from electrical voltage to optical properties. Instead of applying high voltage to make the filament detectable electrically, the system uses laser illumination and detects changes in optical transmission, reflection, or absorption that occur when the laser interacts with the filament region, enabling detection at low electrical stress conditions

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 rapid and non-invasive localization of resistive memory filaments, facilitating the measurement of numerous devices and creation of solid statistics on filament formation, while minimizing stress on the device and preserving its electrical characteristics.

Implementation Method 1

acquiring an image indicating a location of a filament formed in a RRAM cell device using an impinging laser beam stimulus

Methodology Applied

Scientific EffectLaser stimulation: Laser

Implementation Method 2

using an impinging laser signal to localize the filament at a very low device bias voltage

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11901002B2RRAM filament spatial localization using a laser stimulation

Publication Date: 2024.02.13 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

System and method to localize a position of an RRAM filament of resistive memory device at very low bias voltages using a scanning laser beam. The approach is non-invasive and allows measurement of a large number of devices for creating statistics relating to the filament formation. A laser microscope system is configured to perform a biasing the RRAM cell with voltage (or current). Concurrent to the applied bias, a laser beam is generated and aimed at different positions of the RRAM cell (e.g., by a raster scanning). Changes in the current (or voltage) flowing through the cell are measured. The method creates a map of the current (or voltage) changes at the different laser positions and detects a spot in the map corresponding to higher (or lower) current (or voltage). The method determines the (x,y) position of the spot compared to the edge/center of the RRAM cell.