MTJ Under Layer Segmentation for Thermal Stability

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Solution Overview

Problem

Current memory devices face challenges in achieving improved switching characteristics and thermal stability due to metal diffusion issues and the need for enhanced magnetic properties in variable resistance elements, particularly in magnetic tunnel junction (MTJ) structures.

Innovation Solution

The implementation of a semiconductor memory device with a magnetic tunnel junction (MTJ) structure that includes a silicon-based alloy under layer, a heavy metal under layer, and an amorphous blocking layer to prevent metal diffusion and improve perpendicular magnetic anisotropy and tunneling magnetoresistance, featuring a magnetic correction layer to offset stray magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional MTJ structure is used, then the device is simple to manufacture, but metal diffusion occurs and thermal stability is poor

Engineering Contradiction:

Improvethermal stabilityVSAvoidunder layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The under layer is divided into multiple distinct layers: a first under layer with perpendicular magnetic anisotropy, a blocking layer to prevent metal diffusion, and a second under layer. This segmentation allows each layer to perform its specific function independently, improving thermal stability while managing the complexity through functional specialization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structures in the under layer, combining materials with different properties (e.g., CoFeB with perpendicular magnetic anisotropy, Ta as a blocking layer, and Ru as another blocking layer) to achieve both thermal stability and prevent metal diffusion simultaneously.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the MTJ structure is optimized for perpendicular magnetic anisotropy, then switching characteristics improve, but metal diffusion increases

Engineering Contradiction:

Improveswitching characteristicsVSAvoidmetal diffusion

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The blocking layer acts as an intermediary between the first under layer and the second under layer, preventing direct contact and metal diffusion while allowing the perpendicular magnetic anisotropy effect to be maintained in the first under layer for improved switching characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The blocking layer is extracted as a separate functional component between the under layers, specifically designed to prevent metal diffusion while allowing the magnetic properties of the first under layer to remain intact for switching operations.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the under layer thickness is increased to improve magnetic properties, then perpendicular magnetic anisotropy enhances, but device area increases

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The first under layer is designed with specific local properties (perpendicular magnetic anisotropy) in a controlled thickness range, while the blocking layer and second under layer provide additional functions without significantly increasing the lateral device area, achieving localized optimization of magnetic properties.

Inventive Principle:

Principle #3Local quality

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 configuration enhances the thermal stability and switching current of the variable resistance element, improving its performance by reducing metal diffusion and maintaining magnetic properties, thereby achieving better data storage characteristics.

Implementation Method 1

a tunnel barrier layer interposed between the free layer and the pinned layer

Methodology Applied

Scientific EffectQuantum tunneling:

Implementation Method 2

improve perpendicular magnetic anisotropy and tunneling magnetoresistance

Methodology Applied

Scientific EffectTunneling magnetoresistance: Magnetoresistance

Implementation Method 3

improve perpendicular magnetic anisotropy

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Data Source

PatentUS9841915B1Electronic device

Publication Date: 2017.12.12 SK HYNIX INC

AI summary

This technology provides an electronic device. An electronic device in accordance with an implementation of this document may include a semiconductor memory for storing data, and the semiconductor memory may include a magnetic tunnel junction (MTJ) structure comprising a free layer having a variable magnetization direction, a pinned layer having a pinned magnetization direction, and a tunnel barrier layer interposed between the free layer and the pinned layer; and an under layer located under the MTJ structure, wherein the under layer may include: a first under layer including a silicon-based alloy; a second under layer including a metal; and a blocking layer interposed between the first under layer and the second under layer and including an amorphous material.