iPMA Cap Layer for Giant Perpendicular Magnetic Anisotropy
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Solution Overview
Problem
Existing magnetic random access memory (MRAM) technologies face challenges in achieving high perpendicular magnetic anisotropy and high magnetoresistive ratio while maintaining thermal stability and uniformity, especially as device sizes shrink and oxygen percentages in tunnel barrier layers decrease, leading to increased magnetic damping and reduced spin polarization.
Innovation Solution
The implementation of a perpendicular magnetoresistive element with a bi-layer iPMA cap layer structure, comprising a rocksalt-crystal iPMA contacting sub-layer and a face-centered cubic or hexagonal close-packed iPMA metal sub-layer, along with a crystal-breaking layer between amorphous CoFeB free layers, to induce giant interfacial perpendicular magnetic anisotropy, optimized through specific deposition techniques and thermal annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the device size is shrunk and oxygen percentage in tunnel barrier layer is decreased, then device miniaturization is achieved, but magnetic damping increases and spin polarization decreases
Solution Approach 1:
The patent introduces an iPMA cap layer with specific crystal structure (FCC or HCP) and composition at the interface with the recording layer to locally enhance perpendicular magnetic anisotropy. This localized structural modification at the interface region compensates for the degradation caused by device miniaturization and reduced oxygen content, maintaining high spin polarization and low damping constants despite overall device shrinkage.
2Ease of manufacture
If conventional single-layer cap structure is used, then manufacturing is simpler, but interfacial perpendicular magnetic anisotropy is insufficient
Solution Approach 1:
The patent employs a composite cap layer structure consisting of multiple layers with different materials and crystal structures (including FCC and HCP phases). This composite structure creates enhanced interfacial perpendicular magnetic anisotropy through the specific arrangement and properties of constituent layers, achieving superior magnetic anisotropy compared to conventional single-layer cap structures.
3Manufacturing precision
If thermal annealing is applied to crystallize the recording layer, then interfacial grain structure matching is improved, but process complexity increases
Solution Approach 1:
The patent performs thermal annealing treatment to crystallize the amorphous recording layer and form well-defined interfacial grain structures before subsequent device assembly and operation. This preliminary crystallization step ensures optimal interfacial grain structure matching between the recording layer and cap layer, which is critical for achieving high perpendicular magnetic anisotropy and device performance.
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 approach enhances interfacial perpendicular magnetic anisotropy, reduces damping constants, and achieves a high magnetoresistive ratio with lower write currents, while maintaining thermal stability and uniformity, enabling efficient and reliable MRAM performance.
Implementation Method 1
induce giant interfacial perpendicular magnetic anisotropy
Implementation Method 2
strong perpendicular magnetic anisotropy (PMA) induced by both interface interaction and crystalline structure
Implementation Method 3
performing a thermal annealing process to accelerate crystallization of the amorphous ferromagnetic film
Implementation Method 4
performing a thermal annealing process to accelerate crystallization
Implementation Method 5
write method using spin momentum transfers, i.e., spin torque transfer (STT) switching technique
Implementation Method 6
magnetic random access memories (MRAMs) using the magnetoresistive effect of ferromagnetic tunnel junctions
Implementation Method 7
SOT (spin-orbit torque) MRAM devices feature magnetization switching of the free layer immediately adjacent to a SOT layer, which is caused by the transverse spin polarized current across the free-layer-SOT-layer interface generated by injecting an in-plane electrical current
Data Source
AI summary
A magnetoresistive element comprises a novel iPMA cap layer on a surface of a recording layer to induce a giant interfacial perpendicular magnetic anisotropy (G-iPMA) of the recording layer and a method of making the same. The recording layer comprises a first free layer immediately contacting to the tunnel barrier layer and having a body-centered cubic structure with a (100) texture, and a second free layer having a body-centered cubic structure with a (110) texture or a face-centered cubic structure with a (111) texture, and a crystal-breaking layer inserted between the first free layer and the second free layer.