Cylindrical MTJ Structure for Uniform Magnetic Switching
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Solution Overview
Problem
Conventional magnetic RAMs experience abnormal phenomena such as vortex pinning and domain wall pinning in the free magnetic layer, leading to increased current requirements for switching and thermal instability, resulting in fail bits and reduced sensing margin.
Innovation Solution
A magnetic memory device with a cylindrical MTJ structure featuring a conductive layer, insulating layer, and multiple magnetic layers, including a pinning layer, pinned layer, tunneling layer, and free magnetic layer, which generates a circular closed magnetic field to prevent abnormal pinning, allowing for uniform and low-current switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional planar MTJ structure is used, then manufacturing is simpler, but vortex pinning and domain wall pinning occur leading to increased current requirements and thermal instability
Solution Approach 1:
The patent applies curvature by transitioning from a planar MTJ structure to a cylindrical MTJ structure. The cylindrical configuration causes the magnetic field to form closed loops around the current path, preventing vortex pinning and domain wall pinning. This curvature transformation resolves the technical contradiction by maintaining manufacturing feasibility while dramatically improving switching uniformity and thermal stability through the elimination of abnormal magnetic phenomena.
Solution Approach 2:
The patent introduces a third dimension by stacking magnetic layers vertically to form a cylindrical structure rather than arranging them in a planar configuration. This dimensional change allows the magnetic field to circulate around the current path in closed loops, preventing pinning phenomena. The vertical stacking maintains compatibility with conventional semiconductor manufacturing processes while achieving superior magnetic switching characteristics.
2Ease of operation
If higher current is applied to overcome pinning, then switching can be achieved, but thermal stability decreases and fail bits increase
Solution Approach 1:
The cylindrical MTJ structure creates a closed-loop magnetic field that efficiently switches the free magnetic layer without requiring excessive current. By eliminating vortex pinning and domain wall pinning through the curved geometry, the structure achieves reliable switching at lower current levels, thereby maintaining thermal stability and reducing fail bits while ensuring ease of operation.
3Use of energy by moving object
If free magnetic layer thickness is reduced to lower switching current, then current requirement decreases, but thermal stability is significantly lowered
Solution Approach 1:
The cylindrical configuration transforms the magnetic field into closed loops that efficiently couple with the free magnetic layer. This allows for reduced free magnetic layer thickness and lower switching current while maintaining thermal stability, because the closed-loop field distribution prevents energy loss to pinning phenomena even in thinner layers.
Solution Approach 2:
The patent changes the geometric parameters of the MTJ structure from planar to cylindrical, which fundamentally alters the magnetic field distribution. This parameter change enables the system to achieve low switching current with thin free magnetic layers without sacrificing thermal stability, as the closed-loop field configuration prevents the formation of unstable magnetic domains.
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 cylindrical MTJ structure ensures stable and uniform switching characteristics with reduced current requirements, minimizing fail bits and maintaining thermal stability, while enhancing the magnetic resistance ratio and sensing margin.
Implementation Method 1
a circular closed magnetic field is generated around a current flow direction according to Oersted's law
Implementation Method 2
The resistance of the MTJ cell varies depending on the magnetization orientations of the magnetic layers formed on and under the tuneling layer. The magnetic RAM utilizes this property of the MTJ cell to store data in the MTJ cell.
Data Source
AI summary
A magnetic memory device includes a magnetic tunneling junction (MTJ) structure having a cylindrical shape. Elements of the MTJ structure are co-axial. The MTJ structure includes a conductive layer, an insulating layer co-axially formed around the conductive layer and a material layer formed around the insulating layer, the material layer being co-axial with the conductive layer and having a plurality of magnetic layers. The material layer includes a lower magnetic layer, a tunneling layer, and an upper magnetic layer that are sequentially stacked around and along the conductive layer.