MRAM Cell With Switching Resistor For Read Margin
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Solution Overview
Problem
Conventional MRAM cells with multilevel state write operations face challenges with small resistance levels, limiting their read margin and ability to store multiple data bits effectively.
Innovation Solution
Incorporating a switching resistant element in the MRAM cell, which can switch between resistance levels when a current is passed through, combined with a magnetic tunnel junction to achieve multiple resistance levels, allowing for improved read margin and multibit storage by varying the junction resistance and switching resistance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional MRAM cells use multilevel state write operations, then data storage capacity increases, but resistance levels become small limiting read margin
Solution Approach 1:
The patent combines a magnetic tunnel junction (MTJ) with a switching resistant element to create a composite memory cell structure. The MTJ provides magnetic state storage while the switching resistant element provides high-contrast resistance levels, merging the advantages of both components to achieve multibit storage with improved read margin.
Solution Approach 2:
The memory cell uses a composite structure combining ferromagnetic layers, tunnel barrier layers, and switching resistant elements. This composite material approach allows the cell to exhibit multiple distinct resistance levels that are easily distinguishable, solving the problem of small resistance levels in conventional multilevel MRAM cells.
2Speed
If magnetic tunnel junction is used to increase performance, then writing and reading speeds improve, but device complexity increases
Solution Approach 1:
The magnetic tunnel junction serves multiple functions: it provides nonvolatile memory storage through magnetic states, enables high-speed reading through magnetoresistance effects, and participates in writing operations through spin transfer torque. This multi-functionality achieves high performance without proportionally increasing complexity.
Solution Approach 2:
The MTJ structure utilizes spin-polarized current to automatically switch its own magnetic state during writing operations, eliminating the need for external magnetic field generation components. The reading operation naturally exploits the magnetoresistance effect inherent to the structure, reducing additional complexity for high-speed operation.
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 solution enhances the read margin and enables the MRAM cell to store at least four different resistance levels, surpassing conventional multibit MRAM cells by combining junction and switching resistances, thus improving data storage capabilities.
Implementation Method 1
magnetic tunnel junctions can have a strong magnetoresistance at ambient temperature
Implementation Method 2
The spin polarized write current 31 is spin polarized such as to induce a local spin torque on the second magnetic layer 23
Implementation Method 3
A first field current 41 is passed in the first current line 4 generating a first magnetic field 42, and a second field current 51 is passed in the second current line 5 generating a second magnetic field 52
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(d)
AI summary
A magnetic random access memory (MRAM) cell (1) comprising: a magnetic tunnel junction (2) comprising a tunnel barrier layer (22) between a first magnetic layer (21) having a first magnetization direction, and a second magnetic layer (23) having a second magnetization direction being adjustable from a first direction to a second direction relative to the first magnetization direction, such as to vary a junction resistance (RMTJ) of the magnetic tunnel junction (2) from a first to a second junction resistance level; wherein said magnetic tunnel junction (2) further comprises a switching resistant element (62, 22) electrically connected to the magnetic tunnel junction (2) and having a switching resistance (Rs) that can be switched from a first to a second switching resistance level when a switching current (31) is passed through the switching resistant element (62, 22), such that a MRAM cell resistance (Rc) of the MRAM cell (1) can have at least four different cell resistance levels depending of the resistance level of the junction resistance (RMTJ) and the switching resistance (Rs). The MRAM cell disclosed herein achieves improved read margin compared to conventional MRAM cells and allows for writing at least four different cell resistance levels.