Active Matrix Substrate With Layered Oxide Semiconductor TFTs
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Solution Overview
Problem
Existing active matrix substrates face challenges in producing oxide semiconductor TFTs with different characteristics for various applications, such as liquid crystal display devices and organic EL display devices, as the same oxide semiconductor film is used, making it difficult to achieve the required performance for pixel and circuit TFTs with distinct functions.
Innovation Solution
The active matrix substrate employs a top gate structure with oxide semiconductor TFTs having different layered structures and mobility characteristics, allowing for the production of TFTs with specific threshold voltages and mobility levels by using a common oxide semiconductor film, enabling the formation of TFTs with distinct characteristics for pixel and circuit applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same oxide semiconductor film is used for both pixel TFTs and circuit TFTs, then manufacturing process simplicity is improved, but the ability to achieve different performance characteristics for different applications deteriorates
Solution Approach 1:
The patent applies local quality by creating different layered structures of oxide semiconductor films in different regions. Specifically, the pixel TFT region uses a multi-layer oxide semiconductor structure with different compositions and mobilities, while the circuit TFT region uses a single-layer or different multi-layer structure. This allows each region to have optimized characteristics for its specific function while using a common manufacturing process that deposits oxide semiconductor films across the entire substrate.
Solution Approach 2:
The patent segments the oxide semiconductor film into multiple layers with different compositions and characteristics. By forming a first oxide semiconductor film with lower mobility and a second oxide semiconductor film with higher mobility, and selectively removing or retaining these layers in different regions, the patent achieves different performance characteristics for pixel TFTs and circuit TFTs while maintaining process simplicity.
2Power
If a top gate structure with thinned gate insulating layer is used, then current supply performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the thickness parameter of the gate insulating layer to achieve thinned structure for improved current supply performance. The gate insulating layer is formed with a thickness of 50 nm or less, which enables higher current supply capability. This parameter change is achieved through standard thin-film deposition techniques, maintaining manufacturing feasibility while improving performance.
Solution Approach 2:
The patent uses composite materials by combining the thinned gate insulating layer with multi-layer oxide semiconductor films. The gate insulating layer is formed using a combination of inorganic insulating films (such as silicon oxide, silicon nitride) and may include organic insulating films, creating a composite structure that achieves both thinness for performance and stability for manufacturing reliability.
3Manufacturing precision
If multiple oxide semiconductor films with different mobilities are stacked, then TFT performance customization is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies local quality by creating different layered structures of oxide semiconductor films in different regions. Specifically, the pixel TFT region uses a multi-layer oxide semiconductor structure with different compositions and mobilities, while the circuit TFT region uses a single-layer or different multi-layer structure. This allows each region to have optimized characteristics for its specific function while using a common manufacturing process that deposits oxide semiconductor films across the entire substrate.
Solution Approach 2:
The patent segments the oxide semiconductor film into multiple layers with different compositions and characteristics. By forming a first oxide semiconductor film with lower mobility and a second oxide semiconductor film with higher mobility, and selectively removing or retaining these layers in different regions, the patent achieves different performance characteristics for pixel TFTs and circuit TFTs while maintaining process simplicity.
Data Source
AI summary
An active matrix substrate includes a first TFT and a second TFT, each of TFTs includes an oxide semiconductor layer and a gate electrode arranged on a part of the oxide semiconductor layer with a gate insulating layer therebetween, in which in the first TFT, the oxide semiconductor layer, in a first region covered with the gate electrode with the gate insulating layer interposed between the oxide semiconductor layer and the gate electrode, has a layered structure including a lower oxide semiconductor film and an upper oxide semiconductor film throughout and a mobility of the upper oxide semiconductor film is higher than a mobility of the lower oxide semiconductor film, and in the second TFT, in at least a part of a first region of the oxide semiconductor layer, of the lower oxide semiconductor film and the upper oxide semiconductor film, one oxide semiconductor film is provided, and another oxide semiconductor film is not provided.