SOT-MRAM Three-Terminal Structure for High Integration

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Solution Overview

Problem

There is a need for spin orbit torque magnetoresistive random access memory (SOT-MRAM) with a three-terminal device structure that achieves high integration and ease of stacking.

Innovation Solution

A magnetic memory with a three-terminal device structure, comprising a plurality of conductive lines, magnetoresistive elements, transistors, and a controller to control voltages during read and write operations, allowing for selective writing and reading of data in a stacked configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional four-terminal device structure is used, then the device can perform basic memory operations, but the degree of integration and ease of stacking are limited

Engineering Contradiction:

Improvedegree of integrationVSAvoidease of stacking

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The memory device is segmented into distinct functional regions: a first conductive line for write current, a second conductive line for read current, and a third conductive line serving as both read path and bit line. This segmentation allows independent optimization of write and read operations while reducing interconnections needed for stacking.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The third conductive line serves multiple functions: it acts as a read current path through the magnetoresistive element and simultaneously as a bit line for selecting memory cells during read operations. This multi-functionality reduces the total number of conductive lines needed, simplifying the device structure for integration and stacking.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of operation

If more conductive lines are added to enable selective write and read operations, then data selectivity improves, but device complexity increases

Engineering Contradiction:

Improveselective writing and readingVSAvoidnumber of conductive lines

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The third conductive line is designed to serve dual purposes: conducting read current through the magnetoresistive element and functioning as a bit line for cell selection. This eliminates the need for separate dedicated read and bit lines, reducing the total conductive line count while maintaining selective read capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The read current path and bit line function are merged into a single third conductive line. During read operations, this line simultaneously provides the read current path and serves as the bit line for selecting which memory cell to read, combining two previously separate functions into one structure.

Inventive Principle:

Principle #5Merging (Combining)

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 proposed solution enables a higher degree of integration and easier stacking of SOT-MRAM, facilitating the selective writing and reading of data while reducing electrical stress on magnetoresistive elements.

Implementation Method 1

a magnetoresistive element arranged between the first conductive layer and the second conductive line and including a first magnetic layer, a second magnetic layer arranged between the first magnetic layer and the second conductive line, and a first nonmagnetic layer arranged between the first magnetic layer and the second magnetic layer

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS12336191B2Magnetic memory including transistors and magnetoresistive elements respectively connected between a conductive plate and a conductive line and additional transistors each connected between the conductive line and another conductive line

Publication Date: 2025.06.17 KIOXIA CORP

AI summary

A magnetic memory includes first conductive lines, a second conductive line, a third conductive line, a fourth conductive line, a conductive layer, magnetoresistive elements, first transistors, a second transistor, and a third transistor. Each magnetoresistive element is arranged between the conductive layer and the second conductive line and includes a first magnetic layer, a second magnetic layer between the first magnetic layer and the second conductive line, and a first non-magnetic layer between the first magnetic layer and the second magnetic layer. Each first transistor is connected between the conductive layer and one of the magnetoresistive elements, and has a gate which is a part of one the first conductive lines. A second transistor is connected between a first end of the second conductive line and the third conductive line. A third transistor is connected between a second end of the second conductive line and the fourth conductive line.