Thin Film Transistor Gate Insulating Film Structure
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Solution Overview
Problem
Conventional thin film transistors face challenges with gate insulating films that have either low dielectric constants, making them unsuitable for low-voltage applications, or high hydrogen content, which can lead to hydrogen penetration into the active layer and excessive electron carrier formation.
Innovation Solution
A thin film transistor substrate with a gate insulating film comprising a high dielectric constant silicon nitride layer formed by plasma-enhanced atomic layer deposition (PEALD) and a lower dielectric constant silicon oxide layer, both with low hydrogen content, to improve film quality and prevent hydrogen penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon oxide is used as the gate insulating film, then the manufacturing process is simple, but the dielectric constant is low making it unsuitable for low-voltage applications
Solution Approach 1:
The patent employs a composite gate insulating film structure consisting of multiple layers with different materials (silicon oxide, silicon nitride, and high-k material layers). This composite structure combines the manufacturing simplicity of silicon oxide with the high dielectric constant of other materials, enabling low-voltage operation while maintaining ease of fabrication through sequential deposition processes.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers of the gate insulating film. The silicon oxide layer provides good interface quality and ease of deposition, while silicon nitride layers provide high dielectric constant in specific regions, and high-k material layers are positioned where maximum electric field control is needed. This localized optimization resolves the contradiction between manufacturing simplicity and low-voltage suitability.
2Reliability
If silicon nitride is used as the gate insulating film, then the dielectric constant is high, but a large amount of hydrogen penetrates into the active layer during manufacturing
Solution Approach 1:
The patent introduces intermediary layers between the silicon nitride layer and the active layer to prevent hydrogen penetration. These intermediary layers act as diffusion barriers that block hydrogen atoms from reaching the active layer while allowing the silicon nitride layer to maintain its high dielectric constant function. This mediator approach resolves the contradiction by preserving the beneficial electrical properties while eliminating the harmful hydrogen contamination.
Solution Approach 2:
The patent segments the gate insulating film into multiple distinct layers, separating the hydrogen-generating silicon nitride layer from the active layer through intermediate barrier layers. This segmentation isolates the harmful hydrogen source while maintaining the functional benefits of silicon nitride, resolving the contradiction between high dielectric constant and hydrogen contamination prevention.
3Device complexity
If a single-layer gate insulating film is used, then the structure is simple, but it cannot simultaneously achieve high dielectric constant and low hydrogen content
Solution Approach 1:
The patent uses composite materials in a multi-layer gate insulating film structure where each layer contributes specific properties. The combination of silicon oxide, silicon nitride, and high-k material layers creates a composite system that achieves both high dielectric constant and low hydrogen content at the interface with the active layer, resolving the contradiction between structural simplicity and performance requirements.
Solution Approach 2:
The patent applies local quality by optimizing different regions of the gate insulating film for different functions. The lower layers use materials optimized for dielectric constant, while upper layers near the active layer use materials optimized for low hydrogen content and good interface quality. This spatial differentiation of material properties resolves the contradiction between structural simplicity and simultaneous achievement of multiple performance targets.
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 enables high driving current at low voltages, prevents excessive electron carrier formation, and enhances the reliability and hysteresis characteristics of the thin film transistor.
Implementation Method 1
silicon nitride formed by plasma-enhanced atomic layer deposition using disopropyl amino silane gas as a source gas
Data Source
AI summary
A thin film transistor substrate and a display apparatus including the same includes a substrate; an active layer and a gate electrode on the substrate, the active layer and gate electrode being spaced apart from each other vertically; a gate insulating film including a first gate insulating film and a second gate insulating film provided between the active layer and the gate electrode; and a source electrode and a drain electrode, each of the source electrode and the drain electrode connected to the active layer. The first gate insulating film is provided closer to the gate electrode than the second gate insulating film, a dielectric constant of the first gate insulating film is higher than a dielectric constant of the second gate insulating film, and a hydrogen content of the first gate insulating film is lower than a hydrogen content of the second gate insulating film.