Oxide TFT Display Structure With Oxygen-Stabilizing Interlayer Wiring
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Solution Overview
Problem
The challenge lies in maintaining the initial characteristics and reliability of Thin Film Transistors (TFTs) using oxide semiconductors over the product life, as the amount of oxygen in the insulating layer affects defect formation and stability, leading to a trade-off between initial performance and long-term reliability.
Innovation Solution
A display device structure featuring a substrate with pixels comprising a first TFT of a first oxide semiconductor, a laminated structure of a second oxide semiconductor and metal for the drain and source wirings, and an interlayer insulating film that supplies and confines oxygen, stabilizing the TFT characteristics without increasing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of oxygen in the insulating layer is increased to improve initial characteristics, then the initial performance is improved, but defects in the insulating layer increase leading to reduced reliability
Solution Approach 1:
The insulating layer is divided into multiple layers: a first insulating layer in contact with the oxide semiconductor layer and a second insulating layer above it. The first insulating layer has lower oxygen content to minimize defects, while the second insulating layer has higher oxygen content to provide oxygen supply, thus segmenting the conflicting requirements of oxygen supply and defect reduction into separate functional layers.
Solution Approach 2:
Different regions of the insulating structure are assigned different oxygen concentrations based on local functional requirements. The first insulating layer near the oxide semiconductor has low oxygen to prevent defect formation at the critical interface, while the second insulating layer farther away has high oxygen to serve as an oxygen reservoir, implementing local quality differentiation to resolve the contradiction.
2Reliability
If the amount of oxygen in the oxide semiconductor is increased to improve initial characteristics, then the initial performance is improved, but oxygen moves out during product life leading to characteristic changes and reduced reliability
Solution Approach 1:
The second insulating layer is pre-loaded with excess oxygen during manufacturing before the product is put into service. This preliminary oxygen supply creates an oxygen reservoir that can compensate for oxygen loss from the oxide semiconductor during the product lifecycle, preventing characteristic degradation without requiring high initial oxygen content in the active semiconductor layer.
Solution Approach 2:
The second insulating layer acts as an intermediary oxygen reservoir between the external environment and the oxide semiconductor layer. It mediates oxygen supply by releasing oxygen to the oxide semiconductor when oxygen depletes, thereby stabilizing the oxygen content and preventing characteristic changes without direct exposure to environmental fluctuations.
3Reliability
If a single insulating layer with high oxygen content is used to supply oxygen, then oxygen supply is improved, but defect formation increases reducing reliability
Solution Approach 1:
The insulating structure is segmented into two distinct layers with different oxygen characteristics. The first insulating layer provides a defect-free interface with low oxygen content, while the second insulating layer provides oxygen supply capability with high oxygen content, thus segmenting the conflicting functions of oxygen supply and defect minimization into separate layers.
Solution Approach 2:
Different oxygen concentrations are assigned to different local regions of the insulating structure based on functional requirements. The region in contact with the oxide semiconductor (first layer) has low oxygen to prevent defect formation, while the upper region (second layer) has high oxygen to ensure oxygen supply, implementing spatial differentiation of oxygen quality.
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 ensures stable oxygen supply to the TFT, maintaining initial performance and reliability by minimizing defect formation in the insulating layer, thus achieving high reliability and consistent characteristics throughout the product life.
Implementation Method 1
an interlayer insulating film that supplies and confines oxygen, stabilizing the TFT characteristics without increasing defects
Data Source
AI summary
The purpose of the present invention is to improve reliability of the TFT of the oxide semiconductor. The feature of the invention is: A display device comprising: a substrate including a display area where plural pixels are formed, the pixel includes a first TFT of a first oxide semiconductor, a first gate insulating film is formed under the first oxide semiconductor, a first gate electrode is formed under the first gate insulating film, an interlayer insulating film is formed on the first oxide semiconductor; a drain wiring, which connects with the first oxide semiconductor, and a source wiring, which connects with the first oxide semiconductor, are formed on the interlayer insulating film; the drain wiring or the source wiring is a laminated structure of a second oxide semiconductor and a first metal, the second oxide semiconductor is under the first metal.