Bonded MRAM Cell Structure With Offset Selector Switching
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Solution Overview
Problem
Magnetoresistive memory devices require flipping of the magnetization direction of the free layer using an external power source for programming, which can be inefficient and may pose challenges in terms of energy consumption and operational complexity.
Innovation Solution
A memory device comprising a memory pillar stack with a bonding interface between a selector pillar structure and a magnetic tunnel junction (MTJ) pillar structure, formed by bonding different portions of the memory cell to each other, including a first and second electrically conductive line with a selector device laterally offset from the MTJ, and incorporating data control circuits and temperature monitoring circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external power source is used to flip the magnetization direction of the free layer for programming, then the memory device can be programmed, but energy consumption increases and operational complexity increases
Solution Approach 1:
The patent employs a selector device with non-linear I-V characteristics that enables self-assisted magnetization switching. The selector device generates a localized voltage drop that assists in flipping the magnetization direction of the free layer without requiring a separate external power source, thereby reducing energy consumption while maintaining programming capability
Solution Approach 2:
The patent combines the selector device and MTJ pillar structure into a single integrated memory cell architecture. The selector device is positioned in series with the MTJ, merging the selection function and storage function into one unified structure, which eliminates the need for additional external power sources and reduces operational complexity
2Reliability
If an external power source is used to flip the magnetization direction of the free layer for programming, then the memory device can be programmed, but device complexity increases
Solution Approach 1:
The selector device automatically provides the necessary voltage assistance for magnetization switching through its inherent non-linear I-V characteristics. This self-service mechanism eliminates the need for complex external power management circuits and simplifies the overall device operation
Solution Approach 2:
By integrating the selector device directly with the MTJ pillar structure in a series configuration, the patent merges multiple functions (selection, storage, and switching assistance) into a single compact unit, thereby reducing device complexity while maintaining full programming 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
Enhances the efficiency and operational simplicity of magnetoresistive memory devices by reducing the need for external power to flip the magnetization direction, thereby optimizing energy usage and operational complexity.
Implementation Method 1
A magnetoresistive memory device can store information employing the difference in electrical resistance of a first configuration in which a ferromagnetic free layer has a magnetization direction that is parallel to the magnetization of a ferromagnetic reference layer and a second configuration in which the free layer has a magnetization direction that is antiparallel to the magnetization of the reference layer
Data Source
AI summary
A method of forming a magnetoresistive random access memory (MRAM) device includes providing a first die containing a selector material layer located over a first substrate, providing a second die containing a MRAM layer stack located over a second substrate, and bonding the first die to the second die.