MRAM Write Reliability via Resistance Change Element
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Solution Overview
Problem
The varying reversing current threshold values across different MTJ elements in spin injection magnetization reversal type magnetic random access memory (MRAM) lead to deteriorated write characteristics, as the current required for magnetization reversal is not consistently achievable.
Innovation Solution
Incorporating an anti-fuse element or an additional MTJ element with a different reversing current threshold value in series or parallel with the MTJ element, allowing for adjustment of the resistance and current flow to ensure effective magnetization reversal, regardless of the initial current threshold value of the MTJ element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spin injection magnetization reversal type MRAM is used, then nonvolatile memory with high-speed operation is achieved, but the reversing current threshold value varies from one MTJ element to another, deteriorating write characteristics
Solution Approach 1:
A resistance change element is introduced as an intermediary component connected in series with the MTJ element. This intermediary element adjusts the current flowing through the MTJ element based on its resistance value, ensuring that the current exceeds the first threshold value for magnetization reversal. The resistance change element acts as a mediator that compensates for variations in MTJ element characteristics, thereby improving write reliability without requiring precise manufacturing control of the MTJ elements themselves.
2Adaptability or versatility
If the reversing current threshold value varies among MTJ elements, then manufacturing tolerances are accommodated, but write characteristics deteriorate due to insufficient current for magnetization reversal
Solution Approach 1:
The resistance change element provides dynamic current adjustment based on the actual resistance value of each MTJ element. By changing the resistance value of the resistance change element in response to variations in MTJ element characteristics, the system dynamically adapts the current flow to ensure reliable magnetization reversal. This dynamic adjustment mechanism allows the system to accommodate manufacturing tolerances while maintaining consistent write performance across different MTJ elements.
3Reliability
If a resistance change element is added to adjust current flow, then write characteristics are improved, but device complexity increases
Solution Approach 1:
The resistance change element serves multiple functions: it adjusts the current flowing through the MTJ element to ensure magnetization reversal, and it can be integrated into existing memory cell architectures with minimal structural modification. By designing the resistance change element to work within the existing transistor and interconnection framework, the patent achieves improved write reliability without proportionally increasing device complexity. The resistance change element becomes a multi-functional component that addresses threshold variation issues while fitting into the overall memory cell design.
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 stabilizes the write current and improves the write characteristics by ensuring sufficient current for magnetization reversal, even in MTJ elements with high reversing current thresholds, thereby enhancing the reliability and consistency of data storage.
Implementation Method 1
a first resistance change element electrically connected to the memory cell element, and having a resistance value which changes on the basis of a second threshold value different from the first threshold value
Implementation Method 2
In a write operation using the spin injection magnetization reversing technique, an electric current is supplied perpendicularly to the film surface of the MTJ element, and the magnetization direction in a recording layer is changed by the direction of this electric current
Implementation Method 3
the magnetization directions in the first fixed layer and the first recording layer take one of a parallel state and an antiparallel state in accordance with a direction of an electric current flowing between the first fixed layer and the first recording layer
Data Source
AI summary
A magnetic random access memory includes a memory cell element which includes a first fixed layer, a first recording layer in which a magnetization direction reverses on the basis of a first threshold value, and a first nonmagnetic layer formed between the first fixed layer and the first recording layer, a first interconnection connected to one terminal of the memory cell element, a transistor whose current path has one end connected to the other terminal of the memory cell element, a second interconnection connected to the other end of the current path, and a first resistance change element electrically connected to the memory cell element, and having a resistance value which changes on the basis of a second threshold value.