Tunneling Magnetoresistive Element With Mg-O Barrier and Ta Sublayer
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Solution Overview
Problem
Tunneling magnetoresistive elements with a small RA (element resistance R×element area A) and high ratio of change in resistance (ΔR/R) have not been effectively realized, particularly with insulating barrier layers made of magnesium oxide (Mg—O), as existing structures fail to optimize the crystal orientation and magnetic coupling for enhanced resistance change.
Innovation Solution
A tunneling magnetoresistive element is designed with a laminated ferrimagnetic structure in the pinned magnetic layer, incorporating a nonmagnetic metal sublayer between ferromagnetic sublayers, and an insulating barrier layer of magnesium oxide (Mg—O), which enhances the magnetization-pinning force and improves the ratio of change in resistance (ΔR/R) while maintaining a small RA, by optimizing the crystal structure and suppressing diffusion during annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the RA (element resistance × element area) is decreased to improve device integration, then the ratio of change in resistance (ΔR/R) also decreases, reducing detection sensitivity
Solution Approach 1:
The patent changes the crystallographic orientation parameter from conventional <100> to <110> in the pinned magnetic layer, and adjusts the thickness parameters of the Mg-O barrier layer and ferromagnetic layers. This parameter optimization enables achieving both small RA value and high ΔR/R ratio simultaneously by modifying the fundamental crystal structure parameters rather than simply scaling dimensions
Solution Approach 2:
The patent employs a composite structure consisting of multiple ferromagnetic sublayers (CoFeB, CoFe) with different magnetic properties, combined with Mg-O barrier layer and Ru interlayer. This composite material system allows independent optimization of each layer's properties to achieve both low resistance and high magnetoresistance ratio
2Reliability
If a Mg-O insulating barrier layer is used to achieve high TMR ratio, then the crystal orientation and interface quality must be precisely controlled, increasing manufacturing complexity
Solution Approach 1:
The patent introduces a Ru interlayer before the Mg-O barrier layer to prepare the interface in advance. This preliminary action of depositing Ru creates a favorable growth substrate that guides the Mg-O layer to form with the desired <110> crystal orientation, thereby simplifying the overall manufacturing process by pre-establishing the crystal growth conditions
Solution Approach 2:
The patent changes the target crystal orientation parameter from <100> to <110> in the Mg-O barrier layer formation process. This parameter change in crystal orientation, combined with optimized deposition conditions, achieves high TMR ratio while being compatible with existing sputtering manufacturing processes
3Device complexity
If the pinned magnetic layer structure is simplified to reduce device complexity, then the magnetization-pinning force decreases, reducing stability
Solution Approach 1:
The patent segments the pinned magnetic layer into multiple ferromagnetic sublayers (CoFeB layer and CoFe layer) separated by Ru interlayers. Each sublayer contributes to the overall magnetization-pinning force through exchange coupling, achieving strong pinning effect while maintaining a modular structure that is manageable in fabrication
Solution Approach 2:
The patent creates a nested structure where Ru interlayers are embedded within the pinned magnetic layer stack, with each Ru layer sandwiched between ferromagnetic sublayers. This nested configuration allows the thinner Ru layers to provide exchange coupling and anisotropy enhancement without significantly increasing the total thickness or complexity of the pinned layer
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 solution effectively increases the ratio of change in resistance (ΔR/R) while maintaining a small RA, improving the magnetic sensing capabilities and reducing noise in magnetic recording devices.
Implementation Method 1
Tunneling magnetoresistive (TMR) elements (i.e., tunnel type magnetic sensing elements) are elements whose resistance changes by utilizing a tunnel effect
Implementation Method 2
the ferromagnetic sublayers are magnetically coupled to each other, and all the ferromagnetic sublayers are magnetized in the same direction
Data Source
AI summary
In a tunneling magnetoresistive element, an insulating barrier layer is made of Mg—O, and a first pinned magnetic layer has a laminated structure in which a nonmagnetic metal sublayer made of Ta is interposed between a lower ferromagnetic sublayer and an upper ferromagnetic sublayer. The nonmagnetic metal sublayer has an average thickness of about 1 Å or more and about 5 Å or less.