LCD Pixel Array Structure Reducing Photomask Count
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Solution Overview
Problem
The high cost of photolithography processes in LCD fabrication necessitates a reduction in the number of photomasks used in the fabrication of TFT array substrates.
Innovation Solution
A pixel array structure for LCDs is designed with a silicon island having doped source and drain areas, multiple gate dielectric and metal layers, and storage capacitors formed without additional photomasks, utilizing chemical vapor deposition and photolithography/etching processes to minimize the number of photomasks required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LCD fabrication processes are used, then complete TFT array substrate functionality is achieved, but the number of photomasks required increases fabrication cost
Solution Approach 1:
The patent combines the formation of multiple structural elements (gate electrodes, storage capacitor electrodes, and transistor electrodes) into a single photomask patternning step. By designing the photomask to define all these components simultaneously through their spatial relationships, the process merges what would traditionally require separate photomasks into one unified step, directly reducing photomask count and fabrication cost
Solution Approach 2:
The single photomask serves multiple functions by defining different structural elements in different regions of the substrate. It simultaneously patterns gate electrodes for transistors, storage capacitor electrodes for data retention, and interconnect structures, making one photomask perform the work of what would traditionally require several specialized masks
2Ease of manufacture
If the number of photomasks is reduced, then fabrication cost decreases, but manufacturing precision may be compromised
Solution Approach 1:
The patent segments the substrate into distinct functional regions (active device area, capacitor area, pixel area) with clearly defined boundaries. Each region is optimized for its specific function, and the segmentation allows the single photomask to pattern different structures in different regions without confusion, maintaining precision by reducing interference between overlapping patterns
Solution Approach 2:
The patent utilizes vertical layering (different z-heights) to resolve potential planar conflicts. By stacking gate electrodes, storage capacitor electrodes, and interconnect structures at different vertical levels, the design allows a single photomask to define all these elements without requiring perfect two-dimensional alignment, as the structures occupy different three-dimensional spaces
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 reduces the number of photomasks needed to five, enhances storage capacitance by series connecting storage capacitors, and improves transistor operation properties, thereby lowering fabrication costs and increasing display performance.
Implementation Method 1
two ends of the silicon island respectively has a doped area to be a source and a drain of a thin film transistor
Implementation Method 2
the first electrode, the second gate dielectric layer and the second electrode constitute a first storage capacitor
Implementation Method 3
A first conductive line is on the dielectric layer and in the first opening and the second opening to connect the data line and the source
Data Source
AI summary
Only five photomasks are used to fabricate a LCD pixel array structure. A gate dielectric layer of the LCD pixel array structure is formed by two deposition steps to increase the storage capacity of the storage capacitor.