Active Matrix Substrate Dielectric Layer Adhesion and Voltage
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Solution Overview
Problem
The use of SOG-based insulating films in AM-EWOD devices can degrade TFT characteristics due to high-temperature calcination, and silicon nitride films may fail to provide sufficient adhesion with fluorine resin layers, leading to peeling and leak issues, while silicon oxide films result in low permittivity and higher actuation voltages.
Innovation Solution
A dielectric layer composed of a silicon nitride film with an oxygen-containing surface layer and a metal-oxide film, such as hafnium oxide, is used, formed by plasma CVD and ALD respectively, to enhance adhesion and reduce actuation voltage, with the metal-oxide film providing high permittivity and leak resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride film is used as the dielectric layer, then the permittivity is high and TFT characteristics are maintained, but the adhesion to the fluorine resin water-repelling layer is insufficient
Solution Approach 1:
The patent applies composite materials by combining silicon nitride film with fluorine-containing adhesion promotion layers (such as fluorosilane-based materials) to create a dielectric layer structure that simultaneously achieves high permittivity from the silicon nitride and sufficient adhesion from the fluorine-containing adhesion promotion layer, resolving the contradiction between these two properties
Solution Approach 2:
The patent introduces fluorine-containing adhesion promotion layers as intermediary materials between the silicon nitride film and the water-repelling layer. These intermediary layers act as a bridge that enhances interfacial adhesion while allowing the silicon nitride to maintain its high permittivity function, thus resolving the adhesion deficiency without compromising the dielectric performance
2Strength
If a silicon oxide film is used as the dielectric layer, then the adhesion is improved, but the permittivity becomes low and actuation voltage increases
Solution Approach 1:
The patent uses composite materials by combining silicon oxide film with fluorine-containing adhesion promotion layers to create a dielectric structure that achieves both good adhesion from the silicon oxide and sufficient permittivity through the composite structure, resolving the contradiction between adhesion and permittivity
Solution Approach 2:
The patent applies local quality by creating different functional zones within the dielectric layer: the silicon oxide region provides adhesion, while fluorine-containing adhesion promotion layers are strategically positioned to enhance interfacial bonding, allowing each region to optimize its local function while contributing to overall device performance
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 achieves excellent adhesion between the dielectric and water-repelling layers, prevents peeling, and lowers actuation voltage while maintaining high insulation and leak resistance, enabling reliable droplet actuation in microfluidic devices.
Implementation Method 1
formed by plasma CVD
Implementation Method 2
formed by plasma CVD and ALD respectively
Implementation Method 3
Electrowetting is a phenomenon where under an applied voltage, a droplet placed on a water-repelling layer that is in turn on a dielectric layer covering an electrode changes its contact angle to the surface of the water-repelling layer
Data Source
AI summary
An active matrix substrate includes: a first substrate; and first electrodes, a dielectric layer covering the first electrodes, and a first water-repelling layer in this sequence on the first substrate, wherein the dielectric layer has a multilayer structure including two or more layers and includes a silicon nitride film and a metal-oxide film between the silicon nitride film and the first water-repelling layer, and the silicon nitride film has an oxygen-containing surface layer region on a surface thereof that is in contact with the metal-oxide film.