Vertical FeFETs Using Transition Metal Dichalcogenide Layers
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Solution Overview
Problem
Ferroelectric field effect transistors (FeFETs) face reliability issues due to uncontrollable depolarization and high electric fields between the ferroelectric dielectric and the channel, affecting their operational reliability.
Innovation Solution
A vertical ferroelectric field effect transistor construction is developed, featuring a transition metal dichalcogenide material encircling an isolating core, with a ferroelectric gate dielectric and conductive gate material, and conductive contacts directly against the transition metal dichalcogenide's lateral sidewalls, reducing depolarization tendencies and high electric field issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a typical thin oxide is used between the ferroelectric dielectric material and the channel, then the device structure is simple and manufacturing is easier, but very high electric fields exist causing reliability problems
Solution Approach 1:
The patent replaces the typical thin oxide interface with a transition metal dichalcogenide (TMDC) material layer. This composite material approach creates a new interface structure that simultaneously achieves atomic-level flatness for easy manufacturing and reduced electric field concentration for improved reliability. The TMDC material serves as both a structural component and a functional element that mitigates the high electric field issue.
Solution Approach 2:
The patent changes the physical and chemical parameters of the interface between the ferroelectric dielectric and the channel. By using TMDC materials with specific properties (lateral wall thickness of 1-7 monolayers, atomic-level flatness), the interface characteristics are optimized to reduce electric field concentration while maintaining manufacturability through conformal deposition processes.
2Device complexity
If conventional FeFET structures are used, then the device fabrication is straightforward, but uncontrollable depolarization occurs causing loss of program state
Solution Approach 1:
The patent introduces transition metal dichalcogenide materials as an additional layer in the FeFET structure. This composite structure, combining TMDC with the ferroelectric dielectric and channel, provides controlled depolarization through the unique properties of TMDC materials, preventing loss of program state while adding only moderate structural complexity.
Solution Approach 2:
The TMDC material layer acts as an intermediary between the ferroelectric dielectric and the channel. This intermediate layer mediates the interaction between these components, providing a controlled interface that prevents uncontrollable depolarization while maintaining the overall functionality of the device. The intermediary layer stabilizes the polarization state without significantly complicating the device 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 enhances the reliability of FeFETs by reducing depolarization and adverse electric field effects, improving their operational stability and performance.
Implementation Method 1
The polarization of the ferroelectric, aligned by applying a programming gate voltage, modifies the conductivity of the semiconductive channel between source and drain for a selected operating gate voltage
Implementation Method 2
A transition metal dichalcogenide material encircles the isolating core and has a lateral wall thickness of 1 monolayer to 7 monolayers
Data Source
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AI summary
A vertical ferroelectric field effect transistor construction comprises an isolating core. A transition metal dichalcogenide material encircles the isolating core and has a lateral wall thickness of 1 monolayer to 7 monolayers. A ferroelectric gate dielectric material encircles the transition metal dichalcogenide material. Conductive gate material encircles the ferroelectric gate dielectric material. The transition metal dichalcogenide material extends elevationally inward and elevationally outward of the conductive gate material. A conductive contact is directly against a lateral outer sidewall of the transition metal dichalcogenide material that is a) elevationally inward of the conductive gate material, or b) elevationally outward of the conductive gate material. Additional embodiments are disclosed.