Single Crystal Ferromagnetic Layer for Magnetic Memory Fabrication
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Solution Overview
Problem
Conventional perpendicular magnetization MTJ elements with polycrystalline or amorphous structures face challenges in achieving high write efficiency and large capacity due to weakened magnetic interactions between crystal grains, leading to variations in magnetic properties and limitations in reaching giga-bit level capacity.
Innovation Solution
A method of fabricating magnetic memory using a stacked structure with at least one ferromagnetic layer having a single crystal structure, including a separation layer, conductive bonding layers, and specific materials like MnGa and MnAl alloys, to enhance magnetoresistive ratio and reduce current density for magnetization switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a magnetic body with polycrystalline structure or amorphous structure is formed directly on transistors by sputtering, then the manufacturing process is simple, but the magnetic interaction between crystal grains is weakened resulting in variations in perpendicular magnetic property
Solution Approach 1:
The patent changes the crystal structure parameter from polycrystalline/amorphous to single crystal, and controls the orientation parameter to be perpendicular to the substrate. This is achieved by using specific single crystal substrates with perpendicular easy axes of magnetization, thereby obtaining uniform perpendicular magnetic properties while maintaining manufacturing feasibility through direct sputtering deposition
Solution Approach 2:
The patent employs composite material structures including single crystal ferromagnetic layers with perpendicular magnetization, combined with specific substrate materials and interface layers. This composite approach ensures both the structural integrity for simple manufacturing and the magnetic property uniformity required for high-performance memory devices
2Quantity of substance
If the size of the memory cell is decreased to increase capacity, then the capacity increases, but the write efficiency of conventional MTJ elements deteriorates
Solution Approach 1:
The patent changes the magnetization orientation parameter from in-plane to perpendicular, which fundamentally alters the switching mechanism. This parameter change enables efficient spin torque transfer switching even in miniaturized cells, allowing capacity increase without sacrificing write efficiency. The perpendicular magnetization configuration provides better scaling behavior for small cell sizes
Solution Approach 2:
The patent implements local quality optimization by ensuring uniform perpendicular magnetic properties at the micro-scale through single crystal structure control. This local uniformity in magnetic characteristics enables reliable switching behavior in individually addressed small memory cells, maintaining write efficiency as capacity scales up
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 results in improved magnetic characteristics, enabling large capacity magnetic memory with low current magnetization switching and reduced variations in perpendicular magnetic properties.
Implementation Method 1
A magnetic random access memory (MRAM) using ferromagnetic tunnel junction showing a tunneling magnetoresistive (TMR) effect
Implementation Method 2
the magnetization of the storage layer is switched by the spin torque transfer from the reference layer (spin torque transfer switching method)
Data Source
AI summary
A method of fabricating a magnetic memory according to an embodiment includes: forming a separation layer on a first substrate; sequentially forming a first ferromagnetic layer, a first nonmagnetic layer, and a second ferromagnetic layer on the separation layer, at least one of the first and the second ferromagnetic layers having a single crystal structure; forming a first conductive bonding layer on the second ferromagnetic layer; forming a second conductive bonding layer on a second substrate, on which a transistor and a wiring are formed, the second conductive bonding layer electrically connecting to the transistor; arranging the first and second substrate so that the first conductive bonding layer and the second conductive bonding layer are opposed to each other, and bonding the first and the second conductive bonding layers to each other; and separating the first substrate from the first ferromagnetic layer by using the separation layer.