Magnetoresistive Memory Stray Field Absorption
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Solution Overview
Problem
In spin transfer torque MRAM with perpendicular magnetization films, the magnetic stray field from the reference layer affects the recording layer, leading to reduced thermal stability and increased variations in write current due to element size variations, and the thin tunnel insulating film is prone to damage during processing, causing insulation breakdown and read current variations.
Innovation Solution
A magnetic random access memory structure with a recording layer and reference layer having perpendicular magnetic anisotropy, where the reference layer and tunnel barrier layer continuously extend over multiple MTJ elements, and a magnetization absorbing layer with in-plane magnetic anisotropy is formed between them to absorb stray fields, reducing magnetic stray field variations and preventing tunnel barrier layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a perpendicular magnetization type MTJ element is used, then the write current is reduced and capacity is increased, but the magnetic stray field from the reference layer increases and thermal stability decreases
Solution Approach 1:
A nonmagnetic layer is introduced as an intermediary between the reference layer and recording layer. This nonmagnetic layer serves as a mediator that physically separates the two magnetic layers, preventing direct magnetic interaction while maintaining the perpendicular magnetization configuration. The nonmagnetic layer acts as a buffer that reduces the harmful magnetic stray field from the reference layer affecting the recording layer, thereby improving thermal stability while preserving the low write current advantage.
2Area of moving object
If the element size is decreased, then the capacity is increased, but the variation in element size increases the variation in magnetic stray field and write current
Solution Approach 1:
The nonmagnetic layer acts as a buffer that decouples the magnetic interaction between reference and recording layers. This intermediary structure reduces the sensitivity of the magnetic stray field to element size variations, thereby stabilizing the write current across different element sizes and reducing variation.
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 minimizes magnetic stray field effects, reduces thermal disturbance and write current variations, and prevents insulation failures in the tunnel barrier layer, enhancing the reliability and stability of the MTJ elements.
Implementation Method 1
a magnetization absorbing layer with in-plane magnetic anisotropy is formed between them to absorb stray fields
Implementation Method 2
a variable magnetization direction, a reference layer having magnetic anisotropy perpendicular to film surface, and an invariable magnetization direction, and a first nonmagnetic layer formed between the recording layer and the reference layer
Data Source
AI summary
According to one embodiment, a magnetic random access memory includes a plurality of magnetoresistance elements. The plurality of magnetoresistance elements each include a recording layer having magnetic anisotropy perpendicular to a film surface, and a variable magnetization direction, a reference layer having magnetic anisotropy perpendicular to a film surface, and an invariable magnetization direction, and a first nonmagnetic layer formed between the recording layer and the reference layer. The recording layer is physically separated for each of the plurality of magnetoresistance elements. The reference layer and the first nonmagnetic layer continuously extend over the plurality of magnetoresistance elements.