Self-Aligned MRAM Stack for Multi-Bit Storage
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Solution Overview
Problem
Conventional methods for forming multiple bit memory cells in magnetic random access memories (MRAMs) lack efficient techniques for achieving desired spacing and junction angles in data storage layers, leading to suboptimal switching currents and potential misalignment of memory cells.
Innovation Solution
A method and system for fabricating magnetic memory cells with self-aligned data storage layers, where desired spacing and junction angles are determined and achieved through a magnetoresistive stack deposition and masking process, allowing for distinct switching currents and improved alignment of free layers within the memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional multi-bit memory cells are formed by depositing multiple MTJs with different masks, then multiple bits can be stored in a single stack, but the alignment precision and spacing control between data storage layers deteriorate
Solution Approach 1:
The patent segments the magnetic memory cell into multiple independent data storage layers (first data storage layer and second data storage layer) within a single magnetoresistive stack. Each layer can be independently controlled to have different switching currents, allowing multi-bit storage while maintaining precise alignment through the shared stack structure rather than using multiple separate MTJ deposits with different masks.
Solution Approach 2:
The patent transitions from a conventional planar multi-MTJ approach to a vertical stacking architecture where multiple data storage layers are arranged in the vertical dimension within a single stack. This dimensional change allows multiple bits to be stored while maintaining precise alignment through the inherent vertical stacking geometry, eliminating the alignment issues associated with lateral mask-based fabrication.
2Quantity of substance
If data storage layers are closely spaced to increase density, then storage capacity increases, but switching current control and layer differentiation deteriorate
Solution Approach 1:
The patent applies local quality by creating different switching current characteristics in different data storage layers within the same stack. The first data storage layer has a first switching current and the second data storage layer has a second switching current, allowing each layer to be independently addressed and controlled despite their close vertical proximity, thus maintaining reliability while increasing density.
3Quantity of substance
If multiple masks are used to define different MTJs, then multi-bit storage is achieved, but manufacturing complexity and process steps increase
Solution Approach 1:
The patent merges multiple data storage layers into a single magnetoresistive stack structure, eliminating the need for multiple separate MTJ fabrication processes with different masks. By combining the functionality of multiple MTJs into one integrated stack with vertically stacked data storage layers, the invention simplifies the manufacturing process while maintaining multi-bit storage capability.
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 approach enables the creation of memory cells with multiple bits, where each data storage layer has a unique switching current, reducing inadvertent switching and enhancing the performance and reliability of the memory cells by ensuring precise alignment and geometry differences.
Implementation Method 1
A magnetoresistive stack including layers for each of the memory cells is deposited
Implementation Method 2
A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction. As a result, layer(s) having magnetic moments that are responsive to the spin torque may be switched to a desired state.
Implementation Method 3
Magnetic memories, particularly magnetic random access memories (MRAMs), have drawn increasing interest due to their potential for high read/write speed, excellent endurance, non-volatility and low power consumption during operation. An MRAM can store information utilizing magnetic materials as an information recording medium.
Data Source
AI summary
A magnetic device including memory cells is provided. Each memory cell can store multiple bits corresponding to multiple data storage layers. Desired spacing(s) and desired junction angle(s) for the data storage layers are determined in each memory cell. The desired junction angle(s) and the desired spacing(s) correspond to spin transfer switching currents for the data storage layers having. A magnetoresistive stack including plurality of layers for each of the memory cells is deposited. The memory cells include the data storage layers. A data storage layer layers is spaced apart from nearest data storage layer(s) by a distance corresponding to the desired spacing(s). A mask corresponding to the memory cells is provided on the layers. The memory cells are defined such that each memory cell has the desired junction angle(s) and the desired spacing(s) and such that the data storage layers for each of the memory cells is self-aligned.