Magnetoresistive Element iPMA Cap Layer Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In advanced technology nodes, achieving high interfacial perpendicular magnetic anisotropy in magnetoresistive elements while maintaining a high MR ratio and thermal stability is challenging, especially when reducing MTJ CD size, as thinner MgO tunnel barrier layers and increased Boron-absorbing layer thickness can lead to degraded MR ratios and increased damping constants.
Innovation Solution
The introduction of a specialized iPMA cap layer with a close-packed crystal structure and a rocksalt or simple crystal structure, combined with a thin MgO film and a Ru layer, induces giant interfacial magnetic anisotropy energies, achieving ultra-high interfacial perpendicular magnetic anisotropy and reducing the importance of volume perpendicular magnetic anisotropy, allowing for a thinner Boron-absorbing layer and lower write currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the MgO tunnel barrier layer is made thinner to reduce MTJ CD size, then device miniaturization is achieved, but the MR ratio deteriorates
Solution Approach 1:
The patent applies local quality by creating a CoFeB layer with spatially varying Boron concentration - higher at interfaces with MgO layers and lower in the center region. This local compositional variation optimizes both the interfacial perpendicular magnetic anisotropy (iPMA) at the interfaces and the MR ratio in the bulk, resolving the contradiction between miniaturization and performance maintenance.
2Reliability
If the Boron-absorbing layer thickness is increased to improve perpendicular magnetic anisotropy, then thermal stability is improved, but the damping constant increases
Solution Approach 1:
The patent uses local quality by concentrating Boron atoms at the CoFeB-MgO interfaces through the Boron-absorbing layer, creating high Boron concentration zones only where needed for iPMA enhancement. The center region maintains low Boron concentration to preserve low damping constant, thus achieving thermal stability improvement without excessive energy loss.
3Reliability
If a thick Boron-absorbing layer is used to increase perpendicular magnetic anisotropy, then thermal stability factor is improved, but write current increases due to higher damping constant
Solution Approach 1:
The patent implements local quality by creating Boron concentration gradients that are high at the interfaces (for thermal stability) and low in the bulk (for low write current). This spatially selective Boron distribution allows the system to achieve high thermal stability factor while maintaining low damping constant and thus low write current requirements.
4Volume of moving object
If the MgO tunnel barrier layer is made thinner to maintain reasonable MTJ resistance, then device miniaturization is achieved, but it becomes more difficult to achieve high perpendicular magnetic anisotropy and high MR ratio simultaneously
Solution Approach 1:
The patent applies local quality by creating a CoFeB layer with non-uniform Boron concentration distribution - high Boron concentration at the MgO interfaces to generate strong iPMA and low Boron concentration in the center to maintain high MR ratio. This local compositional control enables simultaneous achievement of high perpendicular magnetic anisotropy and high MR ratio even with thinner MgO barrier layers.
Solution Approach 2:
The patent uses parameter changes by varying the Boron concentration parameter within the CoFeB layer as a function of position. By controlling the Boron concentration gradient during fabrication, the patent optimizes both iPMA and MR ratio parameters independently, enabling high performance in miniaturized devices with thin MgO barriers.
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, maintains high MR ratios, and reduces damping constants, resulting in improved thermal stability and write performance in spin-transfer-torque MRAM devices.
Implementation Method 1
there has been suggested a write method (spin torque transfer switching technique) using spin momentum transfers. According to this method, the magnetization direction of a recording layer is reversed by applying a spin-polarized current along a specific direction to the magnetoresistive element.
Implementation Method 2
accelerate crystallization of the amorphous ferromagnetic film to match interfacial grain structure to both MgO tunnel barrier layer and MgO cap layer through a thermal annealing process.
Implementation Method 3
a typical rocksalt-MgO (100)/bcc-CoFe(100) texture occurs at the interface of a CoFeB layer and an MgO layer, which generates an interfacial perpendicular magnetic anisotropy (iPMA).
Implementation Method 4
The introduction of a specialized iPMA cap layer with a close-packed crystal structure and a rocksalt or simple crystal structure, combined with a thin MgO film and a Ru layer, induces giant interfacial magnetic anisotropy energies, achieving ultra-high interfacial perpendicular magnetic anisotropy
Data Source
AI summary
A magnetoresistive element comprises a novel iPMA cap layer on a surface of a ferromagnetic recording layer. The iPMA cap layer introduces giant interfacial magnetic anisotropy energies (G-iMAE) on the interface between the recording layer and the iPMA cap layer, yielding a giant interfacial perpendicular magnetic anisotropy (G-iPMA) of the recording layer.