Ferroelectric FET Diffusion Barrier Oxygen Gradient
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Solution Overview
Problem
Existing ferroelectric field effect transistors face challenges in maintaining a large memory window due to variations in threshold voltage, which affects the performance of logic devices and memory devices.
Innovation Solution
Incorporating a diffusion barrier layer with a specific oxygen and nitrogen concentration gradient, and a silicon concentration gradient, between the ferroelectric layer and the gate electrode, to enhance the memory window by reducing oxygen penetration and increasing charge trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ferroelectric field effect transistor structure is used, then the device can operate with ferroelectric properties, but the memory window is limited due to oxygen penetration and insufficient charge trapping
Solution Approach 1:
The gate dielectric layer is segmented into multiple functional sub-layers: interfacial layer, diffusion barrier layer with concentration gradient, and optional tunnel barrier layer. This segmentation allows each layer to perform a specific function (interface protection, oxygen diffusion blocking, charge trapping) thereby achieving a large memory window while maintaining manageable structural complexity
Solution Approach 2:
The diffusion barrier layer is designed with non-uniform local composition - specifically, an oxygen concentration gradient where the oxygen concentration decreases from the gate electrode interface toward the ferroelectric layer. This local quality variation optimizes oxygen diffusion blocking at the critical interface while maintaining appropriate electrical properties throughout the layer
2Reliability
If the threshold voltage is stabilized, then the memory window increases, but this requires precise control of oxygen concentration and charge trapping mechanisms
Solution Approach 1:
The diffusion barrier layer is prepared in advance with a predetermined oxygen concentration gradient profile before device operation. This preliminary action of creating the concentration gradient during manufacturing ensures that oxygen diffusion is passively controlled without requiring complex real-time adjustments during device operation, thereby achieving threshold voltage stability with manageable manufacturing precision
Solution Approach 2:
The diffusion barrier layer utilizes controlled parameter changes in composition - specifically, a gradient in oxygen concentration (and potentially nitrogen or silicon concentrations) through the layer thickness. This parameter change creates varying diffusion barriers and charge trapping characteristics at different depths, enabling precise control of the threshold voltage and memory window
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 diffusion barrier layer effectively increases the memory window, improving the performance of ferroelectric field effect transistors, memory devices, and neural network devices by stabilizing threshold voltages and enhancing charge storage capabilities.
Implementation Method 1
the diffusion barrier layer includes SiON, has an oxygen concentration gradient that decreases from a first surface of the diffusion barrier layer facing the gate electrode toward a second surface of the diffusion barrier layer facing the ferroelectric layer
Implementation Method 2
enhancing the memory window by reducing oxygen penetration and increasing charge trapping
Data Source
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AI summary
A ferroelectric field effect transistor includes a channel, a gate electrode provided to face the channel, a ferroelectric layer provided between the channel and the gate electrode, an interfacial layer provided between the channel and the ferroelectric layer, and a diffusion barrier layer provided between the ferroelectric layer and the gate electrode, wherein the diffusion barrier layer includes SiON, the diffusion barrier layer has an oxygen concentration gradient that gradually decreases from a first surface of the diffusion barrier layer facing the gate electrode toward a second surface of the diffusion barrier layer facing the ferroelectric layer, and the diffusion barrier layer may have a nitrogen concentration gradient that gradually increases from the first surface toward the second surface.