Series MTJ Memory Cell Layout for Polymorphic Storage States
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Solution Overview
Problem
Existing MRAM storage technologies are limited to recording two states (0 and 1) due to the difference in high and low resistance of magnetic tunnel junctions, restricting data storage capacity.
Innovation Solution
Implementing a storage unit with first and second magnetic tunnel junctions (MTJs) connected in series, where currents with different directions and magnitudes flow through them, allowing for polymorphic storage by combining different resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single magnetic tunnel junction (MTJ) is used for storage, then the device structure is simple, but the storage capacity is limited to two states (0 and 1)
Solution Approach 1:
The storage unit is divided into multiple magnetic tunnel junctions (first MTJ and second MTJ) with different resistance values. Each MTJ can independently contribute to the total resistance state, enabling the system to represent more than two states. This segmentation allows the storage capacity to expand from 2 states to 4 or more states while maintaining a relatively modular and manageable structure.
Solution Approach 2:
Multiple magnetic tunnel junctions are combined in a single storage unit, where their resistance values are merged to create composite resistance states. The first MTJ and second MTJ work together to produce four distinct resistance statuses, effectively combining their individual binary states into a polymorphic storage system that achieves higher capacity without requiring proportionally more complex external circuitry.
2Productivity
If multiple magnetic tunnel junctions are used to increase storage capacity, then the storage efficiency improves, but the manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the magnetic tunnel junctions, specifically varying the resistance values of different MTJs through controlled adjustments in their structural parameters (such as layer thickness or material composition). This allows the first MTJ and second MTJ to have distinct resistance characteristics that can be precisely tuned during manufacturing, enabling polymorphic storage states while maintaining compatibility with existing fabrication processes.
3Quantity of substance
If more MTJs are used to achieve eight or sixteen resistance statuses, then the storage capacity increases, but the device area increases
Solution Approach 1:
The patent transitions from binary (2-state) storage to polymorphic (4-state, 8-state, or 16-state) storage by adding another dimension of resistance variation. Instead of simply adding more storage elements in parallel, the invention exploits the dimensional space created by combining multiple resistance values in series, effectively packing more information into the same physical footprint by utilizing resistance as an additional encoding dimension.
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 storage efficiency by increasing resistance statuses from four to eight or sixteen, reducing volume and manufacturing costs, and optimizing space utilization.
Implementation Method 1
a magnetoresistive random access memory (magnetic random access memory, MRAM) is a new nonvolatile memory technology
Implementation Method 2
the MRAM stores information by using a change of a magnetic polarization direction
Implementation Method 3
the magnetization direction is inverted by spin-polarized electrons
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
AI summary
Embodiments of this application provide a storage unit and a related device. A first electrode of a first MTJ included in the storage unit is connected in series to a first electrode of a second MTJ by using a first metallic wire. The first electrode of the first MTJ and the first electrode of the second MTJ are electrodes of the same layer. Currents with different directions and different magnitudes flow through the first MTJ and the second MTJ, thereby changing a resistance status of the first MTJ and/or the second MTJ. In this way, polymorphic storage may be implemented by using a combination of different resistance values of the first MTJ and the second MTJ, thereby improving storage efficiency of a memory.