Perpendicular MTJ Devices Maintaining PMA During Annealing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Perpendicular magnetic tunnel junction (MTJ) devices face challenges in maintaining amorphous perpendicular magnetic anisotropy (PMA) characteristics during annealing, which is crucial for achieving a high magnetic resistance (MR) ratio, as most amorphous rare earth transition metal alloys crystallize and lose their PMA at annealing temperatures around 300°C.

Innovation Solution

The development of perpendicular MTJ devices with a multi-layered structure incorporating amorphous rare earth-transition metal (RE-TM) layers and a magnesium oxide (MgO) tunneling layer, where at least one of the pinned or free layers remains amorphous during annealing, ensuring the PMA characteristics are maintained up to higher temperatures, thereby maintaining a high MR ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If amorphous rare earth transition metal alloys are used to maintain PMA characteristics, then perpendicular magnetic anisotropy is achieved, but the materials crystallize during annealing at 300°C and lose their PMA characteristics

Engineering Contradiction:

ImprovePMA characteristicsVSAvoidamorphous status

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent employs composite material structures including CoFeB/MgO/CoFeB tunnel junctions with rare earth transition metal alloys (such as CoFeTa, CoFeW, CoFeMo) combined with MgO tunnel barriers. This composite approach allows the system to maintain PMA characteristics through the amorphous RE-TM layers while the MgO provides structural stability during annealing, resolving the contradiction between achieving PMA and maintaining amorphous status at elevated temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes parameter changes by controlling the thickness, composition, and crystallization temperature of different layers. By adjusting the MgO layer thickness and the RE-TM alloy composition, the system achieves coherent tunneling at lower temperatures while maintaining PMA characteristics through controlled crystallization behavior, allowing annealing without complete loss of amorphous properties.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If annealing is performed at 300°C to ensure high MR ratio, then coherent tunneling is achieved, but most amorphous RE-TM alloys crystallize and lose PMA

Engineering Contradiction:

ImproveMR ratioVSAvoidannealing temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies local quality by creating distinct regions with different thermal and magnetic properties within the MTJ structure. The MgO tunnel barrier and RE-TM magnetic layers have locally optimized compositions and thicknesses that allow different parts of the structure to undergo different transformations during annealing, enabling high MR ratio through coherent tunneling while preserving PMA in specific amorphous regions.

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 approach allows the perpendicular MTJ devices to maintain PMA characteristics up to at least 360°C, ensuring a substantially high magnetic resistance ratio through coherent tunneling, even after annealing, by crystallizing specific layers according to the MgO structure without affecting the amorphous status of the RE-TM layers.

Implementation Method 1

at least one of the pinned layer and the free layer has a multi-layered structure including an amorphous perpendicular magnetic anisotropy (PMA) material

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy (PMA): Anisotropy

Implementation Method 2

uses coherent tunneling in order to obtain a substantially high magnetic resistance (MR) ratio

Methodology Applied

Scientific EffectCoherent tunneling:

Implementation Method 3

the RE-TM layer contacts the MgO layer and is crystallized according to a crystallization structure of the MgO layer

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS8411498B2Magnetic tunnel junction devices, electronic devices including a magnetic tunneling junction device and methods of fabricating the same

Publication Date: 2013.04.02 SAMSUNG ELECTRONICS CO LTD

AI summary

Perpendicular magnetic tunnel junction (MTJ) devices, methods of fabricating a perpendicular MTJ device, electronic devices including a perpendicular MTJ device and methods of fabricating the electronic device are provided, the perpendicular MTJ devices include a pinned layer, a tunneling layer and a free layer. At least one of the pinned layer and the free layer includes a multi-layered structure including an amorphous perpendicular magnetic anisotropy (PMA) material.