MRAM Storage Element with Coercive Force Enhancement Layer
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Solution Overview
Problem
Existing spin torque MRAM technologies face challenges in increasing anisotropy energy and thermal stability while scaling down the size of the storage element, as increasing the thickness of the magnetic layer reduces coercive force and makes it difficult to maintain sufficient resistance to thermal fluctuations.
Innovation Solution
A storage element configuration with a storage layer having perpendicular magnetization, a fixed magnetization layer, an interlayer, a coercive force enhancement layer formed of Cr, Ru, W, Si, or Mn, and a spin barrier layer formed of an oxide, where the magnetization is reversed using spin torque magnetization reversal, enhancing coercive force and anisotropy energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the thickness of the magnetic layer is increased to increase anisotropy energy, then the anisotropy energy increases, but the coercive force is reduced
Solution Approach 1:
The patent employs a composite magnetic layer structure consisting of multiple sub-layers with different magnetic properties. Specifically, it uses a CoFeB layer combined with CoFe layers, where each layer contributes differently to the overall magnetic characteristics. This composite structure enables simultaneous achievement of high anisotropy energy and high coercive force, resolving the trade-off between these two parameters that plagues single-layer structures.
Solution Approach 2:
The patent applies local quality by creating distinct regions within the magnetic layer with different functional properties. The CoFeB layer provides perpendicular magnetic anisotropy and high anisotropy energy, while the CoFe layers provide high coercive force. By spatially separating these functions within the layer structure, the patent optimizes both parameters locally while achieving global performance improvement.
2Quantity of substance
If the size of the storage element is reduced to increase storage density, then the storage density increases, but the thermal stability is reduced
Solution Approach 1:
The composite magnetic layer structure with CoFeB and CoFe layers creates enhanced magnetic anisotropy and coercivity that scales favorably with device size reduction. The synergistic interaction between different magnetic layers maintains thermal stability even as the overall element size decreases, enabling high-density storage without sacrificing reliability.
Solution Approach 2:
The patent changes the magnetic parameters by utilizing materials with different saturation magnetizations and anisotropy energies. The CoFeB layer contributes high perpendicular anisotropy energy density, while the CoFe layers provide high coercivity. This parameter optimization allows the magnetic moment to remain sufficiently large for thermal stability even when the physical volume is reduced for higher density.
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 enables a nonvolatile memory with sufficient thermal stability and high-density information storage even when the element is reduced in size, by increasing coercive force and anisotropy energy, thus improving the reliability and power efficiency of the storage device.
Implementation Method 1
the magnetization of the storage layer is reversed using a spin torque magnetization reversal which is caused by a current flowing in a lamination direction of a layer structure including the storage layer, the interlayer, and the fixed magnetization layer
Implementation Method 2
an interface anisotropy-type perpendicular magnetic layer using the perpendicular magnetic anisotropy which is developed at the crystal interface between Fe and an oxide has attracted attention
Data Source
AI summary
A storage element includes a storage layer having a magnetization perpendicular to a layer surface and storing information according to a magnetization state of a magnetic material; a fixed magnetization layer having the magnetization as a reference of the information of the storage layer and perpendicular to the layer surface; an interlayer formed of a nonmagnetic material and interposed between the storage layer and the fixed magnetization layer; a coercive force enhancement layer adjacent to the storage layer, opposite to the interlayer, and formed of Cr, Ru, W, Si, or Mn; and a spin barrier layer formed of an oxide, adjacent to the coercive force enhancement layer, and opposite to the storage layer. The storage layer magnetization is reversed using spin torque magnetization reversal caused by a current in a lamination direction of a layer structure including the storage layer, the interlayer, and the fixed magnetization layer, thereby storing information.