3D NAND Memory Selector Resistivity Switching
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Solution Overview
Problem
Current three-dimensional NAND memory devices face challenges in efficiently managing resistivity states in selector elements, which affects the selective activation and deactivation of memory strings, leading to inefficiencies in programming and reading operations.
Innovation Solution
A three-dimensional memory device is designed with an alternating stack of insulating and conductive layers over a substrate, featuring vertical memory strings that include a series connection of memory stack structures and two-terminal selector elements capable of providing multiple resistivity states, allowing for selective activation and deactivation of memory strings by setting the selector elements to low or high resistivity states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If selector elements are used to activate/deactivate memory strings, then selective access to memory strings is improved, but leakage current increases when selector elements are in high resistivity state
Solution Approach 1:
The selector element dynamically switches between low resistivity state (for active memory string access) and high resistivity state (for deactivation), with the patent optimizing the high resistivity state to minimize leakage current while maintaining effective switching capability
Solution Approach 2:
The patent modifies the resistivity parameter of the selector element by using specific material compositions (such as titanium oxide with oxygen vacancy control) and processing conditions to achieve a high resistivity state that minimizes leakage while still allowing effective switching to low resistivity state
2Productivity
If multiple resistivity states are provided in selector elements, then programming and reading efficiency is improved, but device complexity increases
Solution Approach 1:
The selector element automatically manages its own resistivity states through inherent material properties and simple voltage application, eliminating the need for complex external control circuitry. The material naturally transitions between resistivity states based on applied voltage, providing self-regulating behavior
Solution Approach 2:
The patent uses material property changes (such as oxygen vacancy concentration in titanium oxide) to create multiple stable resistivity states that can be reliably switched and maintained, providing multi-level memory functionality through controlled parameter modification
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 configuration enhances the selective activation of memory strings, reduces leakage current, and improves the efficiency of programming and reading operations by effectively managing resistivity states, thereby boosting the overall performance of the memory device.
Implementation Method 1
Each of the selector elements includes a two terminal device that is configured to provide at least two different resistivity states
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive word line layers located over a substrate, and a plurality of vertical memory strings. Each vertical memory string includes a series connection of a memory stack structure and a selector element. Each of the memory stack structures extends through the alternating stack and includes a respective memory film and a respective vertical semiconductor channel. Each of the selector elements includes a two terminal device that is configured to provide at least two different resistivity states.