Cross-Point SOT-MRAM Layout With Remote MTJ Read Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Spin-Orbit Torque (SOT) MRAM devices face integration density issues due to their larger footprint compared to Spin Transfer Torque (STT) MRAM, and they require separate write and read paths to maintain device endurance and read stability, which complicates integration and operation.
Innovation Solution
A cross-point SOT-MRAM cell design is implemented, featuring a first and second Spin Hall Effect (SHE) write line that are non-colinear, a cross-point free layer with dielectric isolation, and a remote sensing Magnetic Tunnel Junction (MTJ) to enable independent write and read operations without the need for STT-assisted writing, allowing for true cross-point architecture and improved integration density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SOT-MRAM device configuration is used with separate write and read paths, then device endurance and read stability are improved, but footprint area increases significantly
Solution Approach 1:
The patent merges the write and read paths by using the same Magnetic Tunnel Junction (MTJ) for both operations. The cross-point free layer serves as both the write target and the read sensor, eliminating the need for separate write and read MTJs. This consolidation reduces the device footprint while maintaining the reliability benefits of separate write/read operations through the cross-point architecture's inherent selectivity.
Solution Approach 2:
The cross-point free layer performs multiple functions: it acts as the write target when current flows through the write line, and as the read sensor when current flows through the bit line. This multi-functionality allows a single structure to replace what would traditionally require separate dedicated components for writing and reading, thereby reducing the overall device area.
2Ease of operation
If conventional SOT-MRAM requires two driver transistors, one word line, one bit line, and one write line per device, then write and read operations can be controlled independently, but integration density decreases
Solution Approach 1:
The patent merges multiple control functions into fewer lines. The cross-point architecture allows the same free layer to be accessed for both write and read operations through different current paths. This reduces the number of required control lines and transistors per memory cell, thereby improving integration density while preserving independent control capability through the cross-point selection mechanism.
3Area of stationary object
If STT-MRAM uses same write/read path, then device footprint is reduced, but read reliability is impaired and write current causes MTJ degradation
Solution Approach 1:
The patent segments the current paths into distinct write and read paths within the cross-point architecture. The write current flows through the write line to the cross-point free layer, while the read current flows through the bit line to the same free layer. This segmentation allows the same physical structure to serve both functions while maintaining separate current paths, preventing write-induced degradation during read operations and preserving read reliability.
Solution Approach 2:
The cross-point free layer acts as an intermediary that receives write current from the write line and read current from the bit line through spatially separated paths. This intermediary structure enables the same component to be written and read without direct interference between write and read currents, maintaining both read reliability and MTJ durability while using a compact footprint.
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 design enables efficient SOT-MRAM integration and operation in a cross-point architecture, improving density and allowing for independent write and read operations, while eliminating the need for STT-assisted writing, thus enhancing device performance and integration capabilities.
Implementation Method 1
A cross-point SOT-MRAM cell includes: a first SHE write line; a second SHE write line non-colinear to the first SHE write line
Implementation Method 2
a remote sensing MTJ located in a vicinity of the cross-point free layer, wherein a free layer sensor of the remote sensing MTJ is in contact with one of the first SHE write line and the second SHE write line
Implementation Method 3
a cross-point free layer comprising a first free layer, a second free layer, and a dielectric layer disposed between the first and the second free layers
Data Source
AI summary
A cross-point SOT-MRAM cell includes: a first SHE write line; a second SHE write line non-colinear to the first SHE write line; a cross-point free layer comprising a first free layer, a second free layer, and a dielectric layer disposed between the first and the second free layers, the cross-point free layer configured to store a magnetic bit and located between and in contact with both the first SHE write line and the second SHE write line; and a remote sensing MTJ located in a vicinity of the cross-point free layer, wherein a free layer sensor of the remote sensing MTJ is in contact with one of the first SHE write line and the second SHE write line.