Hybrid ReRAM-PCM Memory Cell for Symmetric Conductance Switching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing resistive random access memory (ReRAM) and phase change memory (PCM) devices exhibit asymmetrical conductance changes during SET and RESET operations, which are undesirable for neuromorphic computing applications.

Innovation Solution

A hybrid memory cell structure is developed, combining ReRAM and PCM elements electrically in parallel, where ReRAM has gradual conductance change during RESET and abrupt during SET, while PCM has gradual conductance change during SET and abrupt during RESET, resulting in a hybrid cell with complementary conductance changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If ReRAM is used for neuromorphic computing, then abrupt conductance change during SET operation is achieved, but gradual conductance change during RESET operation creates asymmetry

Engineering Contradiction:

Improveconductance change speedVSAvoidconductance symmetry

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent combines ReRAM and PCM memory elements into a hybrid memory cell where ReRAM provides abrupt conductance change during SET operation while PCM provides gradual conductance change during RESET operation, achieving symmetrical conductance behavior required for reliable neuromorphic computing

Inventive Principle:

Principle #5Merging (Combining)

2Speed

If PCM is used for analog computing, then gradual conductance change during SET operation is achieved, but abrupt conductance change during RESET operation creates asymmetry

Engineering Contradiction:

Improveconductance change speedVSAvoidconductance symmetry

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent combines ReRAM and PCM memory elements into a hybrid memory cell where PCM provides gradual conductance change during SET operation while ReRAM provides abrupt conductance change during RESET operation, achieving symmetrical conductance behavior required for reliable analog computing

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If a single memory element (ReRAM or PCM) is used, then device complexity is low, but conductance asymmetry during SET and RESET operations limits neuromorphic performance

Engineering Contradiction:

Improvememory cell structureVSAvoidneuromorphic computing performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent merges ReRAM and PCM memory elements into a hybrid memory cell structure, where the complementary conductance change characteristics of the two materials work together to provide symmetrical SET and RESET operations, enabling reliable neuromorphic computing applications

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses a composite memory structure combining different material systems (ReRAM metal oxide layer and PCM chalcogenide layer) with complementary properties, where each material contributes its advantageous conductance change characteristics to achieve overall symmetrical behavior

Inventive Principle:

Principle #40Composite materials

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 hybrid memory cell achieves a gradual conductance change in both SET and RESET operations, addressing the asymmetry issues of individual ReRAM and PCM devices, enhancing neuromorphic computing performance.

Implementation Method 1

Oxygen vacancies in a metal oxide layer of a ReRAM device are the building blocks of a current conducting filament

Methodology Applied

Scientific EffectConductive filament formation:

Implementation Method 2

Phase change memory (PCM) structures are a type of memory device that is considered for analog computing

Methodology Applied

Scientific EffectPhase change: Phase Change

Data Source

PatentUS12562225B2Hybrid memory for neuromorphic applications

Publication Date: 2026.02.24 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A memory device is provided. The memory device includes a ReRAM memory element, and a PCM memory element that is electrically connected in parallel with the ReRAM memory element.