Oxide TFT Light Shielding Structure for Optical Reliability
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Solution Overview
Problem
Oxide semiconductor thin film transistors are susceptible to reliability deterioration due to external light reflection on the gate electrode or metal lines, which affects their optical reliability.
Innovation Solution
Incorporating a light shielding layer and a gate electrode opening in the thin film transistor structure to minimize internal light reflection and protect the active layer from external light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thin film transistor structure without light shielding is used, then the device can be simpler and easier to manufacture, but external light reflects on the gate electrode or metal lines and deteriorates the oxide semiconductor, causing poor optical reliability
Solution Approach 1:
A light shielding layer is formed at the lower portion of the thin film transistor structure before other layers are deposited. This preliminary light blocking structure prevents external light from reaching and reflecting off the gate electrode or metal lines, thereby protecting the oxide semiconductor from deterioration and improving optical reliability without requiring complex modifications to the rest of the device structure.
Solution Approach 2:
The light shielding layer acts as an intermediary element between the external environment and the sensitive oxide semiconductor. This intermediate layer absorbs or blocks harmful light before it can interact with the gate electrode or metal lines, preventing the harmful reflection that would otherwise deteriorate the oxide semiconductor and compromise device reliability.
2Reliability
If a light shielding layer and gate electrode opening are added to block external light, then optical reliability is improved, but the device structure becomes more complex and manufacturing steps increase
Solution Approach 1:
The light shielding layer is formed as a preliminary structure before depositing the oxide semiconductor and other functional layers. By establishing the light blocking capability early in the manufacturing process, subsequent steps can proceed without additional light shielding measures, simplifying the overall manufacturing complexity despite the added layer.
Solution Approach 2:
The gate electrode is divided by forming a gate electrode opening that removes a portion of the gate electrode. This segmentation allows light to pass through the opening rather than reflecting off the entire gate electrode surface, reducing the harmful effects on the oxide semiconductor while maintaining the electrical functionality of the transistor.
3Reliability
If the gate electrode is modified with an opening to reduce light reflection, then optical reliability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The light shielding layer is formed preliminarily before creating the gate electrode opening. This preliminary light blocking structure reduces the amount of light that can reach the gate electrode, thereby reducing the criticality of the opening's precision. Even if the opening dimensions vary within reasonable tolerances, the preliminary light shielding ensures adequate protection against light-induced deterioration.
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
Enhances the optical reliability of thin film transistors by preventing external light from degrading their electrical characteristics, thereby maintaining stable threshold voltage and performance.
Implementation Method 1
a light shielding layer on the substrate... capable of maximally blocking the external light from impinging on the thin film transistors
Data Source
AI summary
A thin film transistor and a display apparatus including the thin film transistor are discussed. The thin film transistor can include a light shielding layer on at least a portion of a substrate, a buffer layer on the light shielding layer, an active layer on the buffer layer, a gate insulating layer on the active layer, and a gate electrode on the gate insulating layer. A gate electrode opening can be disposed in the gate electrode and is formed by removing a portion of the gate electrode.