Amorphous Zinc Oxide LCD Active Layer with H-Shaped Etch Stopper
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Solution Overview
Problem
Existing liquid crystal display (LCD) devices face challenges with amorphous silicon thin film transistors having low mobility and constant current bias issues, while polycrystalline silicon transistors require high temperature processes and have uniformity problems, and oxide semiconductor transistors are prone to degradation during etching and exposure to environmental factors, leading to device instability and short-circuit defects.
Innovation Solution
The use of an amorphous zinc oxide-based semiconductor as an active layer in LCD devices, combined with an etch stopper structure in the shape of 'H' to protect the active layer and prevent exposure, and a method for fabricating the device that includes forming a gate electrode, gate line, active layer, source and drain electrodes, and data line on an array substrate, with a passivation layer and pixel electrode, to ensure stability and prevent short-circuit defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If amorphous silicon thin film transistors are used as switching devices, then the device can be fabricated in a low temperature process, but the mobility is small and constant current bias conditions are not satisfied
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to amorphous zinc oxide-based semiconductor, which fundamentally alters the electrical properties while maintaining the low-temperature fabrication capability. This material substitution enables both low-temperature processing and high mobility with constant current bias characteristics.
2Reliability
If polycrystalline silicon thin film transistors are used, then high mobility and constant current bias conditions are satisfied, but uniform characteristics cannot be secured and high temperature process is required
Solution Approach 1:
The patent changes the crystalline structure parameter from polycrystalline to amorphous state of zinc oxide-based semiconductor. This eliminates the grain boundary issues that cause non-uniform characteristics in polycrystalline silicon while maintaining high mobility through the superior material properties of zinc oxide.
3Device complexity
If oxide semiconductor is used in bottom gate structure, then the structure is simplified, but the oxide semiconductor degenerates during etching process of source and drain electrodes
Solution Approach 1:
The patent introduces an etch stopper layer as an intermediary protective layer between the oxide semiconductor active layer and the etching process for source and drain electrodes. This etch stopper prevents direct contact between the etchant and the oxide semiconductor, preventing degradation while maintaining the simple bottom gate structure.
Solution Approach 2:
The etch stopper layer is formed beforehand on the oxide semiconductor active layer to provide protective cushioning against the subsequent etching process. This preventive measure ensures the oxide semiconductor is not exposed to degrading conditions during manufacturing.
4Ease of manufacture
If the active layer is exposed during manufacturing processes, then the manufacturing process is simplified, but the active layer deteriorates due to environmental exposure
Solution Approach 1:
The patent applies a protective coating on the oxide semiconductor active layer before the oxide semiconductor is exposed to environmental factors or subsequent manufacturing processes. This preliminary protective action prevents deterioration while allowing the manufacturing process to proceed.
Data Source
AI summary
Disclosed are a liquid crystal display device employing an amorphous zinc oxide-based semiconductor as an active layer, and a method for fabricating the same, whereby device stability can be secured by employing an etch stopper structure and device characteristics can be enhanced by minimizing exposure and deterioration of the active layer excluding content regions by virtue of the design of the etching stopper in a shape like “H”. Also, the liquid crystal display device and the fabrication method thereof can further form a semiconductor pattern and an insulating layer pattern on the intersection between the gate line and the data line, so as to compensate a stepped portion, thereby preventing an occurrence of short-circuit.