Perpendicular Capping Layer Induced Anisotropy in Magnetic Tunneling Junctions
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Solution Overview
Problem
Conventional magnetic tunneling junctions in spin transfer torque random access memories (STT-RAMs) face instability due to thermal fluctuations, which can reverse the magnetization of the free layer, compromising thermal stability and writeability, as a high energy barrier for stability increases the switching current, making it undesirable.
Innovation Solution
The introduction of a perpendicular capping layer between the free layer and the contact in the magnetic tunneling junction, which induces perpendicular magnetic anisotropy without increasing the out-of-plane demagnetization energy, allowing for stable switching with reduced write current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high energy barrier is provided for thermal stability, then thermal stability is improved, but switching current increases
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular orientation by introducing a perpendicular capping layer. This parameter change allows the system to achieve thermal stability through perpendicular magnetic anisotropy energy while reducing the switching current requirement, as the perpendicular configuration enables more efficient spin transfer torque switching
Solution Approach 2:
The patent employs a composite structure consisting of a perpendicular capping layer (e.g., MgO, Al2O3, Ta2O5) combined with the free layer. This composite material system induces perpendicular magnetic anisotropy at the interface, providing both thermal stability and reduced switching current through the combined properties of the capping layer and free layer
2Manufacturing precision
If conventional capping layer is used, then surface quality is improved, but thermal stability is compromised
Solution Approach 1:
The patent changes the orientation parameter of the capping layer from conventional in-plane to perpendicular configuration. This parameter change enables the capping layer to induce perpendicular magnetic anisotropy in the free layer, simultaneously maintaining surface quality improvement while achieving enhanced thermal stability
Solution Approach 2:
The perpendicular capping layer serves as an intermediary that induces perpendicular magnetic anisotropy in the free layer without direct exposure to the top contact. This intermediary layer protects the free layer from contact-induced disorder while providing the necessary perpendicular anisotropy for thermal stability
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 thermal stability while reducing the switching current, making the magnetic memory more suitable for applications like STT-RAM by minimizing the impact of thermal fluctuations and maintaining stability with lower write currents.
Implementation Method 1
a perpendicular capping layer for inducing at least part of the perpendicular magnetic anisotropy in the free layer
Implementation Method 2
Spin transfer torque may be used to write to the conventional MTJ 10. In particular, spin transfer torque rotates the magnetization 21 of the conventional free layer 20
Data Source
AI summary
A magnetic element and a magnetic memory utilizing the magnetic element are described. A contact is electrically coupled to the magnetic element. The magnetic element includes pinned, nonmagnetic spacer, and free layers and a perpendicular capping layer adjoining the free layer and the contact. The free layer has an out-of-plane demagnetization energy and a perpendicular magnetic anisotropy corresponding to a perpendicular anisotropy energy that is less than the out-of-plane demagnetization energy. The nonmagnetic spacer layer is between the pinned and free layers. The perpendicular capping layer induces at least part of the perpendicular magnetic anisotropy. The free layer is switchable between magnetic states when a write current is passed through the magnetic element. The free layer includes ferromagnetic layers interleaved with capping layer(s) such that a ferromagnetic layer resides at an edge of the free layer. The capping layer(s) are configured such that the ferromagnetic layers are ferromagnetically coupled.