Vertical Memory Selector Using Variable Resistive Material
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Solution Overview
Problem
Current memory devices face challenges in achieving high integration density and reliability due to the complexity of selector structures and the need for precise voltage application to access specific memory cells in a cross-point array structure.
Innovation Solution
A vertical memory device is designed with a selector incorporating an ovonic threshold switching (OTS) material, allowing for reversible resistance changes in response to electrical signals, enabling simplified selector structures and efficient voltage application through a cross-point architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a cross-point array structure is used to increase integration density, then more memory cells can be packed into a smaller area, but precise voltage application to access specific memory cells becomes more difficult
Solution Approach 1:
The patent segments the voltage application process into distinct phases: first applying voltage to word lines to activate row of memory cells, then applying voltage to bit lines to select specific cells within the activated row. This segmentation allows precise control of voltage application to target specific memory cells while maintaining high integration density of the cross-point array structure.
2Reliability
If complex transistor structures are used as selectors to improve reliability, then voltage control becomes more precise, but device complexity increases
Solution Approach 1:
The patent extracts the selector function from complex transistor structures and implements it using simpler variable resistive materials. The selector is formed by variable resistive material that changes resistance state in response to voltage applied to word lines, eliminating the need for complex transistor-based selector structures while maintaining reliable voltage control for accessing specific memory cells.
3Device complexity
If variable resistive material is used in the selector to simplify the structure, then device complexity is reduced, but the ability to maintain stable resistance states may be compromised
Solution Approach 1:
The patent applies local quality by using different variable resistive materials with specific resistance characteristics in different locations: the selector variable resistive material is optimized for switching between resistance states in response to word line voltage, while the memory cell variable resistive material is optimized for storing data states. This localized optimization ensures stable resistance states are maintained where needed while simplifying the overall selector structure.
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 provides increased integration density and reliability by allowing for random access to memory cells without the need for complex transistor structures, ensuring efficient voltage application and improved cyclic endurance.
Implementation Method 1
The selector includes a variable resistive material of which an electrical resistive value is reversibly changed in response to an electrical signal
Data Source
AI summary
A vertical memory device includes a memory cell structure extending primarily in a vertical direction. A resistive layer is electrically connected to a first end of the memory cell structure. A selector is electrically connected to a second end of the memory cell structure and includes a variable resistive material of which an electrical resistive value is reversibly changed in response to an electrical signal. A first bit line is located apart from the memory cell structure in the vertical direction with the resistive layer disposed therebetween and is connected to the resistive layer. A second bit line is located apart from the memory cell structure in the vertical direction with the selector disposed therebetween and is connected to the selector. A plurality of word line plates are spaced apart from each other in the vertical direction and overlapping each other in the vertical direction. Each word line plate at least partially surrounds a portion of a sidewall of the memory cell structure.