Perpendicular MTJ Fixed Layer Segmentation for Thermal Stability
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Solution Overview
Problem
Spin transfer torque magnetic random access memory (STT-MRAM) devices face challenges in maintaining thermal stability of perpendicular magnetic tunnel junctions (MTJs) while minimizing switching current as device size decreases, affecting long-term data retention and scalability.
Innovation Solution
The implementation of a magnetic memory element with a magnetic free layer structure, an insulating tunnel junction layer, a magnetic reference layer structure, an anti-ferromagnetic coupling layer, and a magnetic fixed layer structure, where the magnetic fixed layer includes multiple stacks of a trilayer unit structure with different materials, such as cobalt, chromium, and nickel, to enhance thermal stability and reduce switching current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coercivity of the magnetic free layer is increased to improve thermal stability, then thermal stability is improved, but the switching current increases
Solution Approach 1:
The magnetic fixed layer is divided into multiple sub-layers (first magnetic fixed layer, second magnetic fixed layer, third magnetic fixed layer) with different magnetization directions. This segmentation allows the system to achieve thermal stability through the collective configuration of multiple layers rather than relying on a single high-coercivity layer, thereby reducing the switching current requirement while maintaining reliability.
Solution Approach 2:
The patent employs a composite magnetic layer structure combining multiple magnetic layers with different properties (CoFeB, CoFe, CoFeNi alloys) and non-magnetic spacer layers. This composite structure achieves both thermal stability and low switching current by leveraging the complementary characteristics of different materials in a unified configuration.
2Area of moving object
If the size of the perpendicular MTJ is reduced to improve scalability, then scalability is improved, but thermal stability degrades
Solution Approach 1:
The magnetic fixed layer is divided into multiple sub-layers (first magnetic fixed layer, second magnetic fixed layer, third magnetic fixed layer) with different magnetization directions. This segmentation allows the system to achieve thermal stability through the collective configuration of multiple layers rather than relying on a single high-coercivity layer, thereby reducing the switching current requirement while maintaining reliability.
Solution Approach 2:
The patent employs a composite magnetic layer structure combining multiple magnetic layers with different properties (CoFeB, CoFe, CoFeNi alloys) and non-magnetic spacer layers. This composite structure achieves both thermal stability and low switching current by leveraging the complementary characteristics of different materials in a unified configuration.
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 achieves thermally stable perpendicular MTJs that can be programmed with low switching current, addressing the scalability and data retention issues in STT-MRAM devices.
Implementation Method 1
a magnetic fixed layer structure formed adjacent to the anti-ferromagnetic coupling layer opposite the magnetic reference layer structure, the magnetic fixed layer structure having a second invariable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to the first invariable magnetization direction
Implementation Method 2
an anti-ferromagnetic coupling layer formed adjacent to the magnetic reference layer structure opposite the insulating tunnel junction layer
Implementation Method 3
The insulating tunnel junction layer 54 is normally made of a dielectric material with a thickness ranging from a few to a few tens of angstroms. When the magnetization directions 60 and 58 of the magnetic free layer 52 and reference layer 50 are substantially parallel, electrons polarized by the magnetic reference layer 50 can tunnel through the insulating tunnel junction layer 54, thereby decreasing the electrical resistance of the perpendicular MTJ 56
Data Source
AI summary
The present invention is directed to an MTJ memory element, which includes a magnetic free layer structure having a variable magnetization direction perpendicular to a layer plane thereof; a tunnel junction layer formed adjacent to the magnetic free layer structure; a magnetic reference layer structure formed adjacent to the tunnel junction layer and having a first invariable magnetization direction perpendicular to a layer plane thereof; an anti-ferromagnetic coupling layer formed adjacent to the magnetic reference layer structure; and a magnetic fixed layer structure formed adjacent to the anti-ferromagnetic coupling layer and having a second invariable magnetization direction that is perpendicular to a layer plane thereof and is opposite to the first invariable magnetization direction. The magnetic fixed layer structure includes multiple stacks of a trilayer unit structure, which includes three layers of different materials with at least one of the three layers of different materials being magnetic.