MRAM Memory Domain Magnetization via Multiferroic Voltage Control

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Solution Overview

Problem

Current Magnetoresistive Random Access Memory (MRAM) technologies face challenges in producing chips with transistor sizes less than 65nm using magnetic field writing to change the magnetization of the free layer.

Innovation Solution

The use of multiferroic elements proximate to memory domains allows for magnetization change via spin torque current, ensuring stability when not writing, and the incorporation of antiferromagnetic and piezoelectric elements to manage domain boundaries and magnetization, enabling independent writing of memory domains with a single current based on voltage application.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If magnetic field writing is used to change the magnetization of the free layer, then the magnetization can be changed, but it becomes difficult to produce MRAM chips with transistor sizes less than 65nm

Engineering Contradiction:

Improvetransistor sizeVSAvoiddifficulty to produce MRAM chips

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the magnetic field writing method with a voltage-controlled magnetization switching mechanism. By applying a voltage to the multiferroic element, the magnetization of the free layer is changed through the magnetoelectric effect, eliminating the need for complex magnetic field generation structures and enabling scaling to smaller transistor sizes below 65nm.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control parameter from magnetic field to voltage. By using voltage to control the magnetization state through the multiferroic element, the system achieves better scalability and manufacturing ease for advanced node transistors, as voltage control is more compatible with standard CMOS fabrication processes at smaller dimensions.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If multiferroic elements are used to change magnetization via spin torque current, then independent writing of memory domains is enabled, but the device complexity increases

Engineering Contradiction:

Improveindependent writing of memory domainsVSAvoiddevice structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent divides the memory line into multiple independently controllable memory domains, each associated with a multiferroic element. By segmenting the control mechanism, each domain can be written independently through voltage application to its corresponding multiferroic element, enabling precise selective writing without affecting other domains.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multiferroic element serves multiple functions: it acts as both the magnetization switching actuator and the stability control mechanism. The same multiferroic element that enables voltage-controlled magnetization switching also provides thermal stability through its anisotropic energy barrier, reducing the need for additional separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach enables stable and independent writing of memory domains, improving the scalability and reliability of MRAM devices by maintaining magnetization stability and allowing for precise control of magnetization direction, thus overcoming the limitations of existing MRAM technologies.

Implementation Method 1

allowing the magnetization of the memory domain to be changed using a spin torque current

Methodology Applied

Scientific EffectSpin torque:

Implementation Method 2

Due to the magnetic tunnel effect, the electrical resistance of the cell changes due to the orientation of the fields in the two plates

Methodology Applied

Scientific EffectMagnetic tunnel effect:

Implementation Method 3

The exchange bias of the antiferromagnetic element may be changed by applying a voltage to the multiferroic element

Methodology Applied

Scientific EffectExchange bias:

Implementation Method 4

a piezoelectric element may be disposed proximate to each memory domain

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS8953366B2Magnetic random access memory device

Publication Date: 2015.02.10 UNIV OF VIRGINIA PATENT FOUND

AI summary

The present invention proposes an electronic memory device comprising a memory line including a memory domain. The memory line may contain a number of memory domains and a number of fixed domains, wherein each memory domain stores a single binary bit value. A multiferroic element may be disposed proximate to each memory domain allowing the magnetization of the memory domain to be changed using a spin torque current, and ensuring the stability of the magnetization of the domain when it is not being written. The domain boundary between the memory domain and one of its adjacent fixed domains may thereby be moved. An antiferromagnetic element may be disposed proximate to each fixed domain to ensure the stability of the magnetization of these. The value of each memory domain may be read by applying a voltage to a magnetic tunnel junction comprising the memory domain and measuring the current flowing through it.