Oxide TFT Display Interlayer Structure for Driver Circuit Stability
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Solution Overview
Problem
Display devices using oxide semiconductor transistors for both pixel and driver circuits face reliability issues due to moisture and hydrogen ingress, leading to degradation of electrical characteristics, especially in high temperature and high humidity environments.
Innovation Solution
A display device structure is implemented with an oxide semiconductor film for the channel formation region, where a planarization film using an organic insulating material is designed to prevent hydrogen or moisture from entering the oxide semiconductor film, particularly in the driver circuit region, by positioning an inorganic interlayer insulating film over the organic insulating film and forming the edge of the third interlayer insulating film on the inner side of the driver circuit region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a transistor using an oxide semiconductor for a semiconductor layer is used to achieve high field-effect mobility and fast operation speed, then the transistor can operate at high speed and be suitable for integrated display devices, but entry of impurities such as hydrogen or moisture into the oxide semiconductor generates carriers and changes electrical characteristics of the transistor
Solution Approach 1:
The patent applies local quality by forming a protective inorganic insulating film specifically over the oxide semiconductor film in regions where impurity protection is most critical. This selective protection approach ensures that the oxide semiconductor maintains its high mobility benefits while being shielded from hydrogen and moisture ingress at the interface with organic insulating materials.
Solution Approach 2:
The patent employs composite materials by combining organic insulating films with inorganic insulating films in a layered structure. The organic insulating film provides bulk insulation while the inorganic insulating film forms a barrier layer that prevents hydrogen and moisture penetration into the oxide semiconductor, creating a composite protection system that addresses both electrical insulation and impurity blocking requirements.
2Strength
If an organic insulating film is formed over the transistor to provide insulation, then electrical insulation is achieved, but hydrogen or moisture from the organic insulating film enters the oxide semiconductor film and changes electrical characteristics
Solution Approach 1:
The patent introduces an inorganic insulating film as an intermediary layer between the organic insulating film and the oxide semiconductor film. This intermediate barrier layer prevents direct contact between the organic material and oxide semiconductor, blocking the diffusion of hydrogen and moisture while maintaining the electrical insulation function of the organic insulating film above it.
Solution Approach 2:
The patent uses thin film structures where an inorganic insulating film is deposited as a thin barrier layer over the oxide semiconductor film. This thin inorganic film acts as a flexible protective shell that effectively blocks impurity ingress while maintaining the overall device structure and electrical performance.
Data Source
AI summary
The display device includes a first substrate provided with a driver circuit region that is located outside and adjacent to a pixel region and includes at least one second transistor which supplies a signal to the first transistor in each of the pixels in the pixel region, a second substrate facing the first substrate, a liquid crystal layer between the first substrate and the second substrate, a first interlayer insulating film including an inorganic insulating material over the first transistor and the second transistor, a second interlayer insulating film including an organic insulating material over the first interlayer insulating film, and a third interlayer insulating film including an inorganic insulating material over the second interlayer insulating film. The third interlayer insulating film is provided in part of an upper region of the pixel region, and has an edge portion on an inner side than the driver circuit region.