TFT LCD Pixel Electrode Contact Structure Reducing Resistance
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Solution Overview
Problem
The conventional contact structure between the pixel electrode and conductive lines in TFT LCDs leads to high electrical resistance, current leakage, and the occurrence of dark or bright spots due to material reactions, which are not effectively mitigated by reducing photolithography cycles without increasing costs.
Innovation Solution
A method involving a transparent substrate with specific metal layers and insulation layers, where the pixel electrode is directly connected to the gate insulating layer through a patterned etching process, reducing the thickness of the gate insulating layer and eliminating buffer layers to minimize electrical resistance and current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the conventional contact structure is used with multiple metal layers and buffer layers, then the manufacturing process is simplified, but the electrical resistance at the pixel electrode contact area increases and current leakage occurs
Solution Approach 1:
The patent removes the second metal layer (Al layer) and buffer layers (amorphous silicon and semi-conductive ohmic layer) from the pixel electrode contact area, extracting only the necessary first metal layer (Ti layer) to maintain electrical contact. This extraction eliminates the harmful reactions between ITO and Al while preserving manufacturing simplicity.
Solution Approach 2:
The patent applies different structural configurations to different areas: in the pixel electrode contact area, only the first metal layer is exposed, while in other areas, the conventional multi-layer structure with buffer layers is maintained. This local differentiation resolves the electrical contact issues without compromising overall manufacturing efficiency.
2Productivity
If photolithography cycles are reduced to minimize costs, then manufacturing efficiency increases, but the contact interface quality between pixel electrode and conductive lines deteriorates
Solution Approach 1:
The patent performs preliminary patterning of the metal layers during the same photolithography cycle used for TFT fabrication, so that the pixel electrode contact area structure is established in advance. This preliminary action allows the contact interface quality to be maintained without requiring additional photolithography cycles.
3Ease of manufacture
If buffer layers are retained in the pixel electrode contact area, then manufacturing is easier, but material reactions occur between ITO and Al leading to high electrical resistance
Solution Approach 1:
The patent converts the potential harm of having no buffer layer (direct ITO-Al contact) into a benefit by selectively removing the Al layer in the contact area, leaving only the Ti layer. This transformation eliminates the harmful ITO-Al reaction while maintaining ease of manufacture through the same fabrication process.
Data Source
AI summary
A method for manufacturing a pixel electrode contact structure of a thin-film transistors liquid crystal display is disclosed. First, a transparent substrate having a first insulating layer thereon is provided. Afterward, a first metal layer and a second metal layer are sequentially formed on the substrate and then be patterned by a halftone technology and an etching process, wherein the second metal layer is removed within the pixel electrode contact area. In the meantime, the drain lines of the thin-film transistor comprising the first metal layer and the second metal layer are formed. Next, a patterned passivation layer is formed on the substrate. Finally, a pixel electrode layer directly connecting the first metal layers within the pixel electrode contact structure is formed on the substrate. This invention provides the pixel electrode contact structure with low contact resistance and prevents the current leakage from the drain line to the storage capacitor.