STT-MRAM MTJ Structure for Lower Free-Layer Switching Current

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The high current requirement for flipping the free layer in a magnetic tunnel junction (MTJ) of spin transfer torque magnetic random access memory (STT MRAM) due to the strong stray field generated by the pinning layer, which affects power consumption and durability.

Innovation Solution

Incorporating a first magnetic structure with a specific magnetization direction relative to the pinning layer to cancel the magnetic field at the free layer, reducing the current needed for flipping and improving durability by minimizing the impact of stray fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a pinning layer with strong stray field is used to pin the reference layer magnetization, then the reference layer magnetization direction is firmly pinned, but the free layer generates a large compensation field requiring increased current for flipping

Engineering Contradiction:

Improvereference layer magnetization pinning stabilityVSAvoidcurrent required for flipping free layer

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

A non-magnetic layer is introduced as an intermediary between the pinning layer and the free layer. This intermediary layer transmits the pinning effect to the reference layer while blocking or reducing the transmission of stray magnetic fields to the free layer, thereby resolving the contradiction between maintaining reference layer pinning stability and reducing the compensation field that increases free layer switching current

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The magnetic tunnel junction structure is segmented into distinct functional layers: a pinning layer for establishing the reference magnetization, a non-magnetic intermediary layer to control field transmission, and a free layer for data storage. This segmentation allows independent optimization of each layer's function, enabling strong reference layer pinning while minimizing the harmful stray field impact on the free layer

Inventive Principle:

Principle #1Segmentation

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

Reduces the current required for flipping the free layer, enhances power efficiency, and extends the lifespan of the MTJ by mitigating the effects of stray fields.

Implementation Method 1

an included angle between a magnetization direction of the first magnetic structure and the magnetization direction of the pinning layer is (90°, 180°]. Because the included angle between the magnetization direction of the first magnetic structure and the magnetization direction of the pinning layer is (90°, 180°], a magnetic field generated by the first magnetic structure at the free layer can cancel a magnetic field generated by the pinning layer at the free layer

Methodology Applied

Scientific EffectMagnetic field cancellation: Magnetic Field

Implementation Method 2

When the magnetization direction of the free layer is parallel to the magnetization direction of the reference layer, in other words, when the magnetization direction of the free layer is the same as the magnetization direction of the reference layer, the storage unit presents low resistance, and stored information is '0'. When the magnetization direction of the free layer is oppositely parallel to the magnetization direction of the reference layer, in other words, when the magnetization direction of the free layer is opposite to the magnetization direction of the reference layer, the storage unit presents high resistance, and stored information is '1'

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

A spin transfer torque magnetic random access memory (STT MRAM) has gained wide attention because of its advantages such as a high speed, low power consumption, and good COMS (complementary metal-oxide-semiconductor) compatibility. When currents flow through the MTJ in different directions (where the current flows from a fixed layer to the free layer or the current flows from the free layer to the fixed layer), the magnetization direction of the free layer changes accordingly

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS12469536B2Memory and electronic device

Publication Date: 2025.11.11 HUAWEI TECH CO LTD

AI summary

An example memory includes a plurality of storage units and bit lines distributed in an array in a storage area of the memory, where each of the storage unit includes a transistor and a magnetic tunnel junction (MTJ) element connected to the transistor. The MTJ element is disposed on a current transmission path between a source or a drain of the transistor and the bit line. The MTJ element includes a pinning layer, a reference layer, a tunneling layer, and a free layer that are stacked in sequence, and a magnetization direction of the pinning layer is parallel to a stacking direction of layers in the MTJ. The example memory further includes a first magnetic structure disposed on the current transmission path and in contact with the MTJ element. An included angle between a magnetization direction of the first magnetic structure and the magnetization direction of the pinning layer is (90°, 180°].