LCD Active Layer Shielding Pattern Leakage Current
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Solution Overview
Problem
The existing methods for fabricating liquid crystal display (LCD) devices with four mask processes face issues such as leakage current due to exposure of the active layer to a backlight, contamination, and reduced aperture ratio, leading to degraded display quality and increased costs.
Innovation Solution
The solution involves forming a gate line and data line on a substrate to define a pixel region, with a gate electrode, active layer, source and drain electrodes, and a shielding pattern that prevents contamination and exposure to the backlight, thereby reducing leakage current and improving the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the active layer is exposed to form source and drain electrodes in the same mask process, then fabrication time and cost are reduced, but leakage current increases due to backlight exposure and contamination
Solution Approach 1:
The patent divides the formation of source and drain electrodes into separate mask processes from the active layer formation. The active layer is formed first, then source and drain electrodes are formed in subsequent processes, allowing the active layer to be protected from backlight exposure and contamination while maintaining efficient fabrication.
Solution Approach 2:
The active layer is formed in advance before the source and drain electrodes are formed. This preliminary formation allows the active layer to be positioned and protected before the electrode formation process, preventing backlight exposure and contamination that would occur if formed simultaneously.
2Device complexity
If the active layer is exposed to form source and drain electrodes, then fabrication complexity is reduced, but aperture ratio decreases due to contamination and leakage current
Solution Approach 1:
By segmenting the fabrication process into distinct steps for active layer formation and source/drain electrode formation, the patent prevents contamination of the active layer. This segmentation maintains high aperture ratio by ensuring the active layer remains clean and free from defects that would reduce display area.
3Ease of manufacture
If source and drain electrodes are formed in the same mask process as the active layer, then manufacturing cost is reduced, but display quality degrades due to leakage current
Solution Approach 1:
The patent segments the formation processes to form the active layer first, then subsequently form the source and drain electrodes in separate mask processes. This segmentation prevents backlight exposure and contamination of the active layer, eliminating leakage current while maintaining reasonable manufacturing costs through efficient process sequencing.
Data Source
AI summary
A liquid crystal display device includes a gate line and a data line crossing each other to define a pixel region on a substrate, a gate electrode connected to the gate line, a gate insulating layer on the gate electrode, an active layer on the gate insulating layer, source and drain electrodes on the active layer, spaced apart from each other and each having inner sides that face each other, wherein the source electrode is connected to the data line, ohmic contact layers between the active layer and each of the source and drain electrodes, a shielding pattern over the active layer and having outer sides, wherein at least one of the outer sides faces at least one of the inner sides of the source and drain electrodes, and a pixel electrode in the pixel region and connected to the drain electrode.