Hydrogen Barrier Layer for OLED Thin Film Transistors
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Solution Overview
Problem
In organic light emitting display devices, the use of different types of thin film transistors on a single substrate leads to hydrogen diffusion issues, affecting the threshold voltage of oxide semiconductor transistors due to hydrogenation processes and encapsulation unit materials, resulting in reliability concerns.
Innovation Solution
A multi-layer insulation structure is designed for the LTPS and oxide semiconductor thin film transistors, with specific materials and film densities to minimize hydrogen diffusion, and a method of manufacturing that optimizes the activation and hydrogenation processes to reduce hydrogen exposure to the oxide semiconductor transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different types of thin film transistors (LTPS and oxide semiconductor) are applied to a single substrate, then device functionality and performance are improved, but hydrogen diffusion occurs from the LTPS transistor's interlayer insulation layer into the oxide semiconductor transistor's active layer, causing threshold voltage changes and reliability issues
Solution Approach 1:
A hydrogen barrier layer is introduced as an intermediary component between the LTPS thin film transistor and the oxide semiconductor thin film transistor. This barrier layer specifically blocks hydrogen diffusion from the LTPS transistor's interlayer insulation layer into the oxide semiconductor transistor's active layer, preventing threshold voltage shifts while maintaining the functionality of both transistor types on the same substrate.
Solution Approach 2:
The insulation structure is segmented into multiple functional layers: a lower insulation layer adjacent to the LTPS transistor, a hydrogen barrier layer positioned between the transistors, and an upper insulation layer adjacent to the oxide semiconductor transistor. This segmentation allows each layer to perform its specific function, with the barrier layer specifically addressing hydrogen diffusion while other layers provide insulation.
2Ease of manufacture
If inorganic films are formed by low-temperature process for encapsulation, then manufacturing feasibility is improved, but the films contain large amounts of hydrogen that diffuse into the oxide semiconductor active layer, changing threshold voltage
Solution Approach 1:
The hydrogen barrier layer serves as a mediator that allows the use of low-temperature formed inorganic films for encapsulation and insulation without compromising the oxide semiconductor transistor's performance. The barrier layer intercepts hydrogen from these easily manufactured low-temperature films, preventing it from reaching the active layer.
Solution Approach 2:
The hydrogen present in the low-temperature formed inorganic films, which would normally be harmful to the oxide semiconductor transistor, is redirected to serve the LTPS transistor's hydrogenation process. The barrier layer confines hydrogen to the LTPS transistor region where it is beneficial, while protecting the oxide semiconductor transistor from hydrogen exposure.
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
The solution effectively reduces hydrogen diffusion into the active layer of oxide semiconductor transistors, improving their reliability and maintaining the integrity of the threshold voltage, thereby enhancing the overall performance of the organic light emitting display device.
Implementation Method 1
hydrogen contained in an interlayer insulation layer of the LTPS thin film transistor and used for a hydrogenation process of an active layer of the LTPS thin film transistor may be diffused into an active layer of the oxide semiconductor thin film transistor
Implementation Method 2
hydrogen contained in an interlayer insulation layer of the LTPS thin film transistor and used for a hydrogenation process of an active layer of the LTPS thin film transistor
Data Source
AI summary
An organic light emitting display device includes a driving TFT on the substrate, a switching TFT on the substrate, and an organic light emitting diode. The driving TFT includes a first active layer formed of poly-Si, and at least a first part of an interlayer insulation layer on the first active layer. The interlayer insulation layer is formed of a first material including hydrogen. The switching TFT includes a second active layer, at least a second part of the interlayer insulation layer between the first active layer and the second active layer, and at least a part of a gate insulation layer between the second part of the interlayer insulation layer and the second active layer. The gate insulation layer is formed from a second material different from the first material and blocking diffusion of hydrogen from the interlayer insulation layer to the second active layer.