CoFeB Free Layer MRAM for Low Magnetostriction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetoresistance effect devices face challenges in reducing the magnetostrictive constant while maintaining a high MR ratio, particularly with the free ferromagnetism layer's magnetostrictive constant exceeding 1.0×10−6, which affects device operation, and previous attempts to reduce it, such as laminating NiFe films, have not been sufficient.
Innovation Solution
The use of CoFeB and CoNiFeB layers with specific boron and nickel content ranges (21%≦b≦23% and 5%≦a≦17%, respectively) for the free ferromagnetism layer, in conjunction with a MgO barrier layer, to control the magnetostrictive constant below ±1.0×10−6 while maintaining a high MR ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetostrictive constant of the free ferromagnetism layer is reduced, then the anisotropy magnetic field is reduced and device operation is improved, but the MR ratio decreases
Solution Approach 1:
The invention changes the compositional parameters of the free ferromagnetism layer by controlling the content of Co, Fe, and B elements. Specifically, it uses CoFeB alloys with controlled boron content (5-15 at%) and specific Co/Fe ratios to achieve the desired balance between magnetostrictive constant and MR ratio. This parameter optimization allows the magnetostrictive constant to be reduced below 1.0×10−6 while maintaining high MR ratio.
Solution Approach 2:
The invention employs composite material structure with CoFeB alloy layers having specific compositional ratios. The free ferromagnetism layer is designed as a CoFeB alloy with controlled element distribution, creating a composite material that simultaneously achieves low magnetostrictive constant and high MR ratio through optimized compositional architecture.
2Reliability
If the magnetostrictive constant is reduced to below 1.0×10−6, then the anisotropy magnetic field becomes sufficiently small for practical operation, but this requires precise control of the free ferromagnetism layer composition
Solution Approach 1:
The invention establishes specific parameter ranges for the free ferromagnetism layer composition: boron content of 5-15 at%, and controlled Co/Fe ratios. By defining these precise parameter ranges, the invention simplifies the composition control process while ensuring the magnetostrictive constant is reduced to below 1.0×10−6, making the complex requirement manageable through standardized compositional specifications.
3Power
If CoFeB with high MR ratio is used, then the output voltage increases, but the magnetostrictive constant becomes too large affecting device operation
Solution Approach 1:
The invention optimizes the compositional parameters of CoFeB by controlling boron content (5-15 at%) and element ratios to achieve a dual benefit: maintaining high MR ratio for high output voltage while reducing magnetostrictive constant to below 1.0×10−6 for reliable device operation. This parameter optimization resolves the contradiction between power output and operational reliability.
Solution Approach 2:
The invention uses optimized CoFeB alloy composition as a composite material that simultaneously achieves high MR ratio and low magnetostrictive constant. The specific compositional architecture creates a material that provides both high output voltage capability and reliable operation by balancing the opposing requirements through controlled element distribution.
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 effectively reduces the magnetostrictive constant to less than ±1.0×10−6 while maintaining a high MR ratio, ensuring optimal device performance by controlling the anisotropy magnetic field and enhancing the operational stability of magnetoresistance effect devices.
Implementation Method 1
A magnetoresistance effect device has been used for MRAM (Magnetic Random Access Memory) known as a nonvolatile memory, a magnetic head, a magnetic sensor or the like
Implementation Method 2
there is a magnetostrictive constant as one of amounts of measurement to be managed for a good device operation
Implementation Method 3
a Magnesium Oxide (MgO) film was grown up for the barrier layer, and further film structure including the three-layers structure of CoFeB (fixed ferromagnetism layer)/MgO (middle layer)/CoFeB (free ferromagnetism layer)
Data Source
AI summary
A magnetoresistance effect device has a fixed ferromagnetism layer, a free ferromagnetism layer, and a barrier layer sandwiched by these ferromagnetic layers. It is constituted so that CoFeB whose amount of addition of boron B (b: atomic %) is 21%≦b≦23% may be used for the free ferromagnetism layer. In the magnetic resistance effect element, a magnetostrictive constant does not change steeply near the magnetostrictive constant zero. A MR ratio is maintained to be high.