Multi-Gate TFT Pixel Layout for Higher Display Aperture Ratio
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Solution Overview
Problem
In active matrix display devices, increasing the aperture ratio without adding manufacturing steps is challenging, as using materials with high dielectric constants for capacitors can lead to complex opening shapes, promoting EL light-emitting portion shrinkage and requiring complex designs for TFTs and wiring, which complicates the manufacturing process.
Innovation Solution
The design includes a thin film transistor with a channel formation region under the wiring, where the channel width is longer than the channel length, and the channel formation regions are positioned to overlap with the wiring, allowing for a simpler pixel electrode shape and increased aperture ratio without complex designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If materials with high dielectric constant are used for capacitors to increase aperture ratio, then the aperture ratio is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent changes the physical parameters of existing materials (amorphous silicon semiconductor layer and silicon oxide insulating layer) by controlling their thickness and arrangement, rather than introducing new materials. The channel width is increased to 5 μm or more, and the silicon oxide layer thickness is optimized to achieve high aperture ratio while maintaining compatibility with existing manufacturing processes.
Solution Approach 2:
The patent segments the transistor structure into distinct functional layers: amorphous silicon semiconductor layer, silicon oxide insulating layer, and conductive layer. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall simplicity in the manufacturing process.
2Area of moving object
If opening area is increased to improve aperture ratio, then the aperture ratio is improved, but the EL light-emitting portion shrinks due to longer edge length
Solution Approach 1:
The patent resolves the edge length problem by changing the dimensional relationship between the opening and the transistor. The channel width is increased to 5 μm or more, providing sufficient spacing between the opening edges and the EL light-emitting portion, thus eliminating the harmful effect of long edges on the light-emitting area.
3Area of moving object
If channel width is increased to improve aperture ratio, then the aperture ratio is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges that are easy to control manufacturing-wise: channel width of 5 μm or more, and silicon oxide layer thickness of 50 nm to 200 nm. These parameter ranges provide sufficient manufacturing margin while achieving the desired high aperture ratio, thus reducing precision requirements.
Data Source
AI summary
An object is to provide a display device with a high aperture ratio or a semiconductor device in which the area of an element is large. A channel formation region of a TFT with a multi-gate structure is provided under a wiring that is provided between adjacent pixel electrodes (or electrodes of an element). In addition, a channel width direction of each of a plurality of channel formation regions is parallel to a longitudinal direction of the pixel electrode. In addition, when a channel width is longer than a channel length, the area of the channel formation region can be increased.