Multi-bit Memory Cell with Tuned MTJ Critical Currents
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Solution Overview
Problem
The existing NAND-SPIN memory technology faces complexities in manufacturing due to the need for external magnetic fields and complex cross-sectional shapes to achieve different current densities for data writing, limiting its development and integration density.
Innovation Solution
A multi-bit memory cell design featuring a spin-orbit coupling layer with sequentially arranged magnetic tunnel junctions, where the critical currents of magnetization reversals are progressively increased or decreased by controlling the angle and aspect ratio of the tunnel junctions, allowing for different data writing effects without external magnetic fields and complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the spin-orbit coupling layer uses different cross-sectional areas to realize different current densities, then different data can be written, but the structure becomes complex and manufacturing is difficult
Solution Approach 1:
The patent applies local quality by configuring different magnetic tunnel junctions with different critical current densities at specific locations along the spin-orbit coupling layer. Each MTJ is designed with tailored dimensions (width and/or length) to achieve its specific critical current density requirement, allowing differentiated data writing capabilities without varying the overall cross-sectional area of the spin-orbit coupling layer.
Solution Approach 2:
The patent changes the dimensional parameters (width and/or length) of individual magnetic tunnel junctions to adjust their critical current densities. By modifying these geometric parameters rather than the cross-sectional area of the spin-orbit coupling layer, the invention achieves multiple data writing states while maintaining structural simplicity and uniform manufacturing processes.
2Adaptability or versatility
If external magnetic fields are used to achieve different current densities, then data writing is possible, but the manufacturing process becomes complex
Solution Approach 1:
The patent replaces the mechanical/external magnetic field system with an intrinsic material property system. Instead of applying external magnetic fields during manufacturing and operation, the invention uses the inherent magnetic anisotropy and dimensionally-tuned critical current densities of the magnetic tunnel junctions to achieve differentiated data writing, eliminating the need for complex external magnetic field generation and control infrastructure.
3Ease of operation
If more transistors are used in NAND-SPIN structure, then data writing control is improved, but integration density decreases
Solution Approach 1:
The patent makes the spin-orbit coupling layer a multi-functional element that serves both as the control mechanism for data writing and as part of the memory storage structure. By embedding the control functionality directly into the spin-orbit coupling layer's dimensional configuration rather than requiring separate transistor structures, the invention achieves effective data writing control while maximizing integration density.
Solution Approach 2:
The patent merges the control function (previously requiring separate transistors) with the spin-orbit coupling layer itself. The dimensional variations within the spin-orbit coupling layer directly provide the control mechanism for different data writing operations, combining what were previously separate functional elements into a unified structure that improves integration density.
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 simplifies the manufacturing process and structure, enabling efficient data writing and high-density integration by controlling current densities without the need for external magnetic fields, thus enhancing the performance and scalability of NAND-SPIN memory.
Implementation Method 1
The Spin-Orbit Torque MRAM (SOT-MRAM) has attracted wide attentions from the industrial and academic worlds due to its advantages of a fast write speed, a separation of read and write paths and a low power consumption.
Implementation Method 2
The Magnetic Tunnel Junction (MTJ) is a basic memory cell of the magnetic random-access memory.
Data Source
AI summary
The present disclosure provides a multi-bit memory cell, an analog-to-digital converter, a device and a method. The multi-bit memory cell comprises: a spin-orbit coupling layer and a plurality of magnetic tunnel junctions disposed on the spin-orbit coupling layer, the plurality of magnetic tunnel junctions comprising a plurality of first magnetic tunnel junctions; the plurality of first magnetic tunnel junctions are sequentially arranged along a length direction of the spin-orbit coupling layer, and critical currents of reversals of the magnetizations of free layers of the plurality of first magnetic tunnel junctions are progressively increased or decreased in sequence along the length direction. The present disclosure provides a multi-bit memory unit with simple manufacturing process and structure.