Oxide Semiconductor TFTs with Selective Organic Insulating Layer
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Solution Overview
Problem
Semiconductor devices with oxide semiconductor TFTs face challenges in stabilizing threshold voltages due to shifts caused by external moisture, light irradiation, and manufacturing errors, which can lead to operational failures and varying performance across different TFTs.
Innovation Solution
A semiconductor device configuration that includes both TFTs with and without a back-gate electrode, where some TFTs are covered with an organic insulating layer while others are not, allowing for selective control of threshold voltages without increasing the size of the TFTs, thereby maintaining pixel aperture ratio and achieving stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a back-gate electrode is added to control threshold voltage, then threshold voltage stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies universality by making the organic insulating layer serve multiple functions: it acts as both a protective encapsulation layer and a threshold voltage control mechanism. When the organic insulating layer is present, it provides protection and stabilizes threshold voltage; when removed selectively, it enables threshold adjustment without requiring additional back-gate electrodes, thus resolving the contradiction between reliability improvement and device complexity
Solution Approach 2:
The patent changes the physical and chemical parameters of the organic insulating layer (presence/absence, thickness, material composition) to control threshold voltage. By adjusting these parameters, the threshold voltage can be stabilized or modified as needed, achieving reliable threshold control without increasing structural complexity through additional electrodes
2Area of moving object
If the size of TFT is reduced to improve pixel aperture ratio, then manufacturing efficiency and display performance are improved, but threshold voltage control becomes more difficult
Solution Approach 1:
The patent applies local quality by selectively removing the organic insulating layer from specific regions (such as peripheral circuit TFTs) while maintaining it in other regions (pixel TFTs). This localized modification allows different threshold voltage characteristics in different areas of the device, enabling size reduction for improved aperture ratio while maintaining threshold stability where needed
Solution Approach 2:
The patent segments the organic insulating layer into different regions with different functions: some regions retain the layer for threshold stabilization, while other regions have the layer removed to enable threshold adjustment in miniaturized structures. This segmentation allows simultaneous achievement of small size and reliable threshold control
3Reliability
If selective coverage with organic insulating layer is implemented, then threshold voltage control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses the organic insulating layer as an intermediary element that can be selectively applied or removed to control threshold voltage. This intermediary approach simplifies manufacturing compared to direct threshold control methods, as the organic layer can be deposited using standard techniques and then selectively removed through etching or other processes, reducing the precision requirements compared to direct electrode patterning
Data Source
AI summary
A semiconductor device includes, a plurality of oxide semiconductor TFTs including a first gate electrode, a first insulating layer in contact with the first gate electrode, an oxide semiconductor layer opposing the first gate electrode via the first insulating layer, a source electrode and a drain electrode which are connected with the oxide semiconductor layer, and an organic insulating layer covering only some of the plurality of oxide semiconductor TFTs, wherein the plurality of oxide semiconductor TFTs include a first TFT which is covered with the organic insulating layer and a second TFT which is not covered with the organic insulating layer, and the second TFT includes a second gate electrode opposing the oxide semiconductor layer via a second insulating layer, the second gate electrode being arranged to overlap with at least a portion of the first gate electrode with the oxide semiconductor layer interposed therebetween.