Thin Film Transistor Substrate Aperture Ratio
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Solution Overview
Problem
In liquid crystal display devices, the aperture ratio is not increased due to light blocking sections formed by gate electrodes, which also limits precision.
Innovation Solution
A thin film transistor substrate configuration with a gate line, channel section, source section, and drain section formed from oxide semiconductor film, where the drain section has lower resistance than the channel section, and a pixel electrode connected to the drain section through an insulation film that does not overlap the gate electrode, increasing light transmission and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gate electrode is formed from a wide section of the gate line and arranged above the contact hole, then the gate electrode can effectively control the channel section, but the aperture ratio is reduced due to light blocking by the gate electrode
Solution Approach 1:
The gate line is segmented such that the gate electrode is formed only from a part of the gate line, specifically positioned to overlap the channel section. This segmentation allows the gate electrode to maintain its control function while reducing the overall area occupied by light-blocking structures, thereby increasing the aperture ratio.
Solution Approach 2:
The gate electrode is positioned in a specific spatial arrangement where it overlaps the channel section but does not extend over the contact hole area. This dimensional positioning optimizes the electrode's control function while minimizing its interference with light transmission through the pixel area.
2Reliability
If the drain section is formed from conductive material with light blocking property, then the electrical connection is effective, but the light transmission amount is reduced
Solution Approach 1:
The drain section is formed from oxide semiconductor film with controlled resistance characteristics. By adjusting the resistance parameter of the oxide semiconductor film, the drain section achieves effective electrical connection while maintaining light transmission properties, as the oxide semiconductor film can be made transparent or semi-transparent unlike traditional conductive materials.
3Ease of manufacture
If the hole in the insulation film overlaps the gate electrode, then the alignment is simplified, but the aperture ratio is reduced and display precision is compromised
Solution Approach 1:
The insulation film structure is designed with different properties in different regions: in the region where the hole is formed, the insulation film allows light transmission and electrical connection, while in the region where the gate electrode overlaps the channel section, the gate insulating film provides electrical isolation. This local differentiation enables both proper alignment and high display precision.
Solution Approach 2:
The gate insulating film acts as an intermediary layer between the gate electrode and the channel section, providing electrical isolation while allowing the gate electrode to still control the channel through electric field effects. This intermediary structure enables the gate electrode to be positioned close to the channel for effective control without direct contact that would compromise the aperture ratio.
Data Source
AI summary
An array board 11b includes a gate line 19, a TFT 17, a pixel electrode 18, a display pixel PX, and a second interlayer insulation film 27. The TFT 17 includes a gate electrode 17a formed from a part of the gate line 19, a channel section 17d formed from an oxide semiconductor film 24, a source section 17b connected to one end of the channel section 17d, and a drain section 17c connected to another end of the channel section 17d and formed from the oxide semiconductor film 24 having resistance lower than the channel section 17d. The pixel electrode 18 is connected to the drain section 17c. The display pixel PX includes the TFT 17 and the pixel electrode 18. The second interlayer insulation film 27 has a second hole in a position overlapping the pixel electrode and the drain section 17c and not overlapping the gate electrode 17a.