Display Device Driver Circuit Moisture Protection
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Solution Overview
Problem
Transistors with oxide semiconductor layers in display devices face reliability issues due to moisture and hydrogen ingress, leading to fluctuations in electrical characteristics, especially in driver circuit transistors under high-temperature and high-humidity conditions.
Innovation Solution
A display device structure is implemented with a pixel portion and a driver circuit portion, where the driver circuit portion includes an opening portion in an inorganic material layer to prevent moisture and hydrogen from entering the oxide semiconductor layer, using a layered insulating film structure with a silicon nitride film and an acrylic-based resin film to facilitate gas release and reduce unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor layers are used in transistors for driver circuits, then field-effect mobility and operating speed are improved, but reliability deteriorates due to moisture and hydrogen ingress causing threshold voltage shifts
Solution Approach 1:
The patent applies this principle by forming a protective inorganic film layer (such as aluminum oxide, titanium oxide, or silicon oxide) over the oxide semiconductor layer. This thin film acts as a barrier shell that prevents moisture and hydrogen from penetrating into the semiconductor layer, thereby maintaining reliability while allowing the high-speed operation enabled by the oxide semiconductor material to continue
Solution Approach 2:
The patent implements this principle by creating an inert protective environment through the inorganic film that blocks external contaminants (moisture and hydrogen) from reaching the oxide semiconductor layer. The film establishes a protected zone around the semiconductor material, effectively isolating it from harmful atmospheric elements that would otherwise cause threshold voltage shifts and reliability degradation
2Ease of manufacture
If organic materials are used to reduce unevenness in transistors, then manufacturing ease is improved, but harmful factors increase due to moisture release from the organic material under high-temperature and high-humidity conditions
Solution Approach 1:
The patent applies this principle by introducing an inorganic film as an intermediary layer between the organic material and the oxide semiconductor layer. This intermediate film serves as a barrier that prevents moisture released from the organic material under high-temperature and high-humidity conditions from reaching and contaminating the semiconductor layer, thus eliminating the harmful effect while preserving the manufacturing advantages of using organic materials for planarization
3Device complexity
If driver circuits are integrated with pixel transistors on the same substrate, then device complexity is reduced, but reliability deteriorates due to higher electric load on driver circuit transistors making them more susceptible to moisture damage
Solution Approach 1:
The patent implements this principle by applying the protective inorganic film specifically to regions containing driver circuit transistors, which are more susceptible to moisture damage due to higher electric loads. This localized protection strategy allows the integration benefits to be maintained while providing enhanced reliability protection where it is most needed, rather than uniformly protecting all transistor regions
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 structure effectively inhibits the ingress of moisture and hydrogen into the oxide semiconductor layer, stabilizing the electrical characteristics and enhancing the reliability of the transistors, particularly in the driver circuit portion, thereby improving the overall performance and longevity of the display device.
Implementation Method 1
an inorganic material layer which covers the driving transistor and includes a silicon nitride film
Implementation Method 2
an opening portion which is formed in the inorganic material layer... impurities such as moisture contained in the organic material are diffused outside from the opening portion
Data Source
AI summary
To improve the reliability of a transistor as well as to inhibit fluctuation in electric characteristics. A display device includes a pixel portion and a driver circuit portion outside the pixel portion; the pixel portion includes a pixel transistor, a first insulating film covering the pixel transistor and including an inorganic material, a second insulating film including an organic material over the first insulating film, and a third insulating film including an inorganic material over the second insulating film; and the driver circuit portion includes a driving transistor to supply a signal to the pixel transistor, the first insulating film covering the driving transistor, and the second insulating film over the first insulating film, and further includes a region in which the third insulating film is not formed over the second insulating film or a region in which the second insulating film is not covered with the third insulating film.