Stacked Magnetic Memory Cells With Position-Tuned Fe Composition
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Solution Overview
Problem
Existing magnetic memory devices face challenges in optimizing the stacked magnetoresistive elements, leading to performance issues due to differences in heat treatment times and layer thicknesses across memory cells at different heights, resulting in non-uniform characteristics.
Innovation Solution
The magnetic memory device employs a configuration where the thickness of specific layers in the stacked structures of memory cells is adjusted to ensure uniformity in magnetoresistive element properties by varying the thickness of layers such as the storage layer, under layer, sub-magnetic layers, and shift canceling layers across different memory cell positions, optimizing annealing times and layer thicknesses to maintain consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory cells are disposed at different height positions in the same direction to increase integration density, then the degree of integration is improved, but the magnetic properties become non-uniform across memory cells
Solution Approach 1:
The patent applies local quality by making the storage layer thickness vary depending on the vertical position of memory cells. Specifically, memory cells at lower vertical positions have thicker storage layers than those at higher positions. This local variation in layer thickness compensates for the non-uniform magnetic properties that arise from stacking multiple memory cells at different heights, thereby maintaining consistent TMR ratios across all memory cells while achieving high integration density.
2Reliability
If the storage layer thickness is increased to improve magnetic properties, then the magnetoresistive element characteristics are improved, but the device area increases
Solution Approach 1:
The patent implements local quality by varying the storage layer thickness according to the vertical position of each memory cell. Lower memory cells receive thicker storage layers to ensure adequate magnetic properties and TMR ratios, while upper memory cells use thinner storage layers to minimize area consumption. This position-dependent thickness optimization ensures that each memory cell achieves the minimum required magnetic performance without uniformly increasing the device area across all cells.
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 ensures uniform magnetic properties across memory cells, enhancing the performance and reliability of the magnetic memory device by maintaining consistent MR, Hk, and coercive force (Hc) values, thereby achieving desired performance characteristics.
Implementation Method 1
the first magnetic layer includes a storage layer having a magnetization direction variable in a film thickness direction by an applied current and having perpendicular magnetic anisotropy
Implementation Method 2
having a magnetization direction variable in a film thickness direction by an applied current
Implementation Method 3
a magnetoresistive element including a first magnetic layer, a tunnel barrier layer, and a second magnetic layer
Data Source
AI summary
A magnetic memory device including a first memory cell which includes a first stacked structure including a magnetic layer and a second memory cell which is provided on the first memory cell and includes a second stacked structure including a magnetic layer. Each of the first stacked structure and the second stacked structure includes a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction, and a nonmagnetic layer provided between the first magnetic layer and the second magnetic layer. A concentration of iron (Fe) contained in the first magnetic layer included in the first stacked structure and a concentration of iron (Fe) contained in the first magnetic layer included in the second stacked structure are different from each other.