Seamless Oxide Semiconductor Layer for Liquid Crystal Display Devices
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Solution Overview
Problem
The existing manufacturing processes for liquid crystal display devices with indium gallium zinc oxide (IGZO) thin film transistors (TFTs) are complex, leading to increased costs and reduced aperture ratios, and require separate light shielding layers for ultraviolet ray irradiation, which complicates the TFT structure and pixel electrode formation.
Innovation Solution
A simplified TFT structure using a seamless oxide semiconductor layer for both the channel semiconductor layer and pixel electrode, where the pixel electrode is formed by radiating energy rays after the array substrate and color filter substrate are bonded, allowing the pixel electrode to overlap with scanning signal lines through a gate insulating film, and using metal oxides like In, Ga, Zn, Sn, Cu, and Cd to enhance conductivity without affecting the channel semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a seamless oxide semiconductor layer is used for both channel semiconductor layer and pixel electrode, then the TFT structure is simplified and manufacturing cost is reduced, but the electrical conductivity control becomes more challenging
Solution Approach 1:
The patent applies local quality by irradiating only specific regions of the oxide semiconductor layer with ultraviolet rays. The pixel electrode region receives UV irradiation to increase conductivity, while the channel semiconductor layer region is shielded from UV irradiation to maintain its original conductivity characteristics. This selective local treatment allows both regions to have different electrical properties despite being part of the same seamless layer.
Solution Approach 2:
The patent introduces a light shielding layer as an intermediary element to control the UV irradiation process. This light shielding layer selectively blocks UV rays from reaching the channel semiconductor layer while allowing irradiation of the pixel electrode region. The intermediary enables precise spatial control of conductivity modification without requiring separate semiconductor and electrode layers.
2Reliability
If separate light shielding layers are added for ultraviolet ray irradiation, then the channel semiconductor layer is protected from UV damage, but the TFT structure becomes more complex and aperture ratio decreases
Solution Approach 1:
The patent merges the light shielding function with the existing gate electrode structure. The gate electrode, which already exists as part of the TFT structure, is utilized to provide UV shielding to the channel semiconductor layer during pixel electrode formation. This merging eliminates the need for additional dedicated light shielding layers while maintaining protection of the channel region.
Solution Approach 2:
The gate electrode serves multiple functions: it acts as both the control electrode for TFT operation and as a light shielding layer during UV irradiation for pixel electrode formation. This multi-functionality reduces the total number of required layers and simplifies the overall TFT structure while still providing necessary UV protection.
3Ease of manufacture
If the pixel electrode is formed by irradiating the oxide semiconductor layer, then the manufacturing process is simplified, but the conductivity uniformity and precision become harder to control
Solution Approach 1:
The patent replaces mechanical patterning methods with optical irradiation methods for forming the pixel electrode. Instead of using photolithography and etching processes to create the electrode pattern, UV rays are used to directly modify the electrical conductivity of the oxide semiconductor layer. This substitution simplifies the manufacturing process while allowing precise control through optical masking.
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
This approach simplifies the TFT structure, improves aperture ratios, increases pixel resolution without reducing aperture, and stabilizes the conductivity of the pixel electrode, reducing manufacturing costs and eliminating the need for separate light shielding layers.
Implementation Method 1
The semiconductor layer is irradiated with ultraviolet rays from the gate electrode side, to thereby form amorphous source and drain regions having a higher conductivity than that before irradiation
Data Source
AI summary
Provided is a liquid crystal display device, including: an array substrate; a plurality of pixels sectioned by video signal lines and scanning signal lines formed on the array substrate; a TFT arranged for each of the plurality of pixels; and a pixel electrode arranged inside each of the plurality of pixels. The TFT includes a channel semiconductor layer and the pixel electrode that are formed of a seamless layer made of an oxide semiconductor. The pixel electrode has an electrical conductivity larger than an electrical conductivity of the channel semiconductor layer under a state in which a gate voltage is not applied.