STT-MRAM Magnetic Junction Package Structure for Stability

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Solution Overview

Problem

Conventional spin transfer torque random access memories (STT-MRAMs) face high write error rates and instability due to back hopping and cell-to-cell variations in magnetic junctions, making it difficult to achieve and maintain the dual state required for reliable data storage.

Innovation Solution

A magnetic junction design featuring a pinned layer, a nonmagnetic spacer layer, and a free layer with a package structure that encircles at least one of the free and pinned layers, enhancing stability and reducing back hopping through ferromagnetic coupling and optimized lateral dimensions, allowing the free layer to switch between stable magnetic states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional pinned layers and free layers are used in STT-MRAM, then the device can store information using magnetic moments, but the write error rate increases due to back hopping and cell-to-cell variations

Engineering Contradiction:

Improvewrite error rateVSAvoidmagnetic junction structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The magnetic junction is divided into multiple functional layers including a pinned layer, a nonmagnetic spacer layer, and a free layer with different lateral dimensions. The free layer has a smaller lateral footprint than the pinned layer, creating a segmented structure that reduces cell-to-cell variations and mitigates back hopping, thereby improving write reliability without excessive complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The free layer is nested within the lateral boundaries of the pinned layer, with the free layer having a smaller lateral dimension. This nested configuration allows the magnetic moments to be more stable and reduces the harmful demagnetizing fields, leading to lower write error rates while maintaining a manageable device structure

Inventive Principle:

Principle #7Nested doll (Nesting)

2Stability of the object's composition

If conventional magnetic junctions are used, then data storage is achieved, but instability occurs due to back hopping of magnetic moments

Engineering Contradiction:

Improvemagnetic moment stabilityVSAvoiddata storage reliability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The magnetic junction employs asymmetric lateral dimensions where the free layer has a smaller lateral footprint than the pinned layer. This asymmetry creates a more stable magnetic configuration that reduces back hopping events, thereby improving both magnetic moment stability and data storage reliability

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The invention addresses magnetic stability by introducing lateral dimension differences between layers rather than only adjusting vertical thickness. The free layer's reduced lateral dimensions compared to the pinned layer create a more stable magnetic state that resists back hopping, enhancing reliability

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If conventional dual magnetic tunneling junctions are used, then spin transfer torque switching is achieved, but cell-to-cell variations increase write error rates

Engineering Contradiction:

Improvewrite error rateVSAvoidcell-to-cell variations

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The magnetic junction implements local quality differences by giving the free layer a smaller lateral dimension than the pinned layer. This localized dimensional variation at the free layer position reduces sensitivity to manufacturing variations, thereby lowering write error rates without requiring extreme manufacturing precision across the entire device

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

The proposed magnetic junction design significantly reduces write error rates and cell-to-cell variations, improving the reliability and stability of data storage by mitigating back hopping and facilitating easier setting into the dual state, thus enhancing the overall performance of STT-MRAMs.

Implementation Method 1

The package structure(s) are ferromagnetically coupled with the pinned layer

Methodology Applied

Scientific EffectFerromagnetic coupling: Ferromagnetism

Implementation Method 2

A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS9203017B2Method and system for providing magnetic junctions including a package structure usable in spin transfer torque memories

Publication Date: 2015.12.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A method and system for providing a magnetic junction usable in a magnetic device are described. The magnetic includes a pinned layer, a nonmagnetic spacer layer, a free layer, and package structure(s). The pinned layer has a pinned layer perimeter and a top surface. The nonmagnetic spacer layer is on at least part of the top surface and between the pinned and free layers. The free layer has a free layer perimeter. The package structure(s) are ferromagnetic and encircles at least one of the free layer and the pinned layer. The package structure(s) are ferromagnetically coupled with the pinned layer. The magnetic junction is configured such that the free layer is switchable between stable magnetic states when a write current is passed through the magnetic junction.