LTPS-TFT LCD Pixel Structure Four-Mask Manufacturing
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Solution Overview
Problem
Conventional low temperature poly-silicon thin-film transistor liquid crystal display (LTPS-TFTLCD) manufacturing processes require seven masks, leading to high manufacturing costs, complex processes, and reduced yield due to ineffective multilayer structures that compromise transmittance.
Innovation Solution
A method using only four masks to form the pixel structure, simplifying the manufacturing process by eliminating unnecessary layers and improving transmittance, involving steps like forming a poly-silicon layer, dielectric layers, gate electrodes, conductive portions, and a transparent electrode layer, with specific etching and doping processes to create TFT and capacitance structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If seven masks are used in the conventional manufacturing process, then the pixel structure can be formed with complete TFT, capacitor, and pad structures, but the manufacturing cost increases and the process complexity increases
Solution Approach 1:
The patent combines multiple functions into fewer mask steps. Specifically, the first mask simultaneously defines the TFT active area, capacitor area, and pad area. The second mask simultaneously forms the gate electrode pattern and the capacitor electrode pattern in a single exposure step, eliminating the need for separate masking operations for these structures.
Solution Approach 2:
The reduced mask set performs multiple functions. Mask 1 serves as a universal pattern definition mask for all three functional areas (TFT, capacitor, pad). Mask 2 serves as a dual-purpose mask that patterns both the gate electrode and capacitor electrode, making it a multi-functional masking step that replaces multiple conventional masks.
2Manufacturing precision
If seven masks are used in the conventional manufacturing process, then the pixel structure can be formed with complete TFT, capacitor, and pad structures, but the manufacturing time increases
Solution Approach 1:
The patent merges multiple sequential masking operations into fewer parallel or sequential steps. By combining the pattern definition for TFT, capacitor, and pad areas into one mask step, and combining the gate and capacitor electrode patterning into another mask step, the total manufacturing time is reduced while maintaining structural completeness.
Solution Approach 2:
The method performs preliminary pattern definition in the first mask step that establishes all functional areas (TFT active area, capacitor area, pad area) simultaneously. This preliminary action prevents the need for subsequent separate definition steps, thereby reducing overall manufacturing time while ensuring proper structure formation.
3Manufacturing precision
If the conventional multilayer structure is used in the display area, then the TFT, capacitor, and pad structures can be complete, but the transmittance decreases due to ineffective layers
Solution Approach 1:
The patent extracts and removes the ineffective intermediate dielectric layer from the display area after it has served its structural purpose. By taking out this layer that no longer serves a functional purpose, the light transmission path is cleared, improving display transmittance while maintaining the structural integrity of the TFT, capacitor, and pad structures through the remaining necessary layers.
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
Reduces manufacturing costs and time while enhancing transmittance by eliminating ineffective layers, resulting in improved display quality and efficiency.
Implementation Method 1
doping the poly-silicon layer to form a first and a second conductive portions in the poly-silicon layer of the control area and the capacitance area respectively
Implementation Method 2
forming a first patterned photo-resist layer on the control area, capacitance area and pad area
Data Source
AI summary
A method for manufacturing the pixel structure of a liquid crystal display is provided. In comparison to using seven masks in the conventional lithographic processes for the pixel structure, only four masks are required in the manufacturing method of the present invention. Therefore, the cost of manufacturing is reduced. Furthermore, the unnecessary multilayer structures on the display area can be removed in the manufacturing processes, and thus, enhance the transmittance thereof.