Vertical ECRAM Channel Structure for Low-Voltage NAND Scaling
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Solution Overview
Problem
The challenge of reducing the height between unit cells in NAND flash memory devices due to inter-cell interference in charge trap flash (CTF) manner is addressed by implementing an electrochemical random-access memory (ECRAM) device that applies low voltage to a gate electrode, improving integration density.
Innovation Solution
An electrochemical memory device with a channel layer extending vertically, including a semiconductor oxide, a gate electrode, a reservoir layer, and a gate oxide layer, where oxygen dissociation energy varies across different areas of the channel layer, allowing oxygen vacancies to change conductivity through voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge trap flash (CTF) manner is used to implement memory function, then memory function is achieved, but inter-cell interference occurs and height between unit cells cannot be reduced
Solution Approach 1:
The patent replaces the charge trap flash (CTF) mechanism with an electrochemical random-access memory (ECRAM) mechanism. Instead of using electron tunneling to trap charges in a trap layer, the invention uses voltage application to move ions in the channel layer, changing electrical conductivity. This substitution of the underlying physical mechanism eliminates the high voltage requirement and associated inter-cell interference while maintaining memory functionality.
Solution Approach 2:
The patent changes the operational voltage parameter from high voltage (required by CTF) to relatively low voltage (used by ECRAM). By altering the voltage parameter and the underlying mechanism, the invention achieves memory function without the harmful high voltage effects that cause inter-cell interference and prevent height reduction.
2Reliability
If high voltage is applied to gate electrode in CTF manner, then memory function is achieved, but integration density cannot be improved due to height constraints
Solution Approach 1:
The patent substitutes the CTF mechanism with ECRAM mechanism, replacing electron tunneling with ion movement. This substitution allows memory operation at lower voltages, enabling reduced unit cell height and improved integration density while maintaining reliable memory function.
Solution Approach 2:
The patent changes the voltage parameter from high to low, and consequently enables reduction of the height parameter between unit cells. This parameter change allows improved integration density (smaller volume) while preserving the memory function through the alternative ECRAM mechanism.
3Use of energy by moving object
If oxygen dissociation energy is lowered in first channel layer, then voltage requirement is reduced, but manufacturing complexity increases due to spatially varying properties
Solution Approach 1:
The patent applies local quality by creating different oxygen dissociation energies in different spatial regions of the channel layer. The first channel layer has lower oxygen dissociation energy than the second channel layer, allowing voltage reduction in the region where it is most needed while maintaining overall device functionality. This spatial variation in material property enables the energy use improvement.
Solution Approach 2:
The patent uses composite material structure with multiple channel layers having different oxygen dissociation energies. By combining materials or structures with different properties in a layered composite, the invention achieves reduced voltage requirements in critical regions while maintaining manufacturability through systematic material composition.
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 device achieves improved integration density between unit cells while applying relatively low voltage, reducing threshold voltage and enhancing operational efficiency.
Implementation Method 1
applying voltage to a gate electrode such that ions present in a channel layer move and thereby changing the electrical conductivity of the channel layer
Implementation Method 2
exchanging oxygen ions between the channel layer and the reservoir layer by applying a voltage to the gate electrode such that oxygen vacancies in one of the channel layer and the reservoir layer increase
Data Source
AI summary
Provided is an electrochemical memory device including a channel layer extending in a vertical direction, the channel layer including a semiconductor oxide, a gate electrode surrounding at least a portion of a side surface of the channel layer, a reservoir layer between the channel layer and the gate electrode, and a gate oxide layer between the gate electrode and the reservoir layer, and wherein the channel layer includes a first channel layer and a second channel layer, the second channel layer spaced farther apart from the gate electrode than the first channel layer, and an oxygen dissociation energy of the first channel layer may be lower than an oxygen dissociation energy of the second channel layer.