Rugged Capacitor Surface for LCD Aperture Ratio
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in increasing the aperture ratio without reducing the stored charge of capacitors, as the size of auxiliary storing capacitors affects the brightness and display quality, and current methods for increasing capacitance are complex and not suitable for mass production.
Innovation Solution
A method to form a rugged surface on the aluminum metal layer of capacitors using halftone photolithography, allowing for simultaneous manufacturing of thin film transistors and capacitors with increased surface area and capacitance, thereby reducing the capacitor's footprint and enhancing the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of the auxiliary storing capacitor is reduced, then the aperture ratio is improved, but the stored charge of the capacitor cannot be maintained
Solution Approach 1:
The patent transforms the two-dimensional planar capacitor structure into a three-dimensional rugged surface structure by forming bumps or waves on the capacitor's lower plate. This dimensional change increases the effective surface area within the same footprint, allowing the capacitor to maintain higher stored charge despite reduced area, thus resolving the contradiction between aperture ratio and stored charge.
Solution Approach 2:
The patent changes the physical geometry parameter of the capacitor from a flat planar surface to a three-dimensional rugged surface with bumps or waves. This parameter change increases the effective surface area and capacitance per unit area, enabling the capacitor to maintain sufficient stored charge while occupying less area, thereby improving the aperture ratio.
2Quantity of substance
If the surface area of the capacitor is increased to maintain stored charge, then the aperture ratio is reduced, but the complexity of manufacturing methods increases
Solution Approach 1:
The patent merges the capacitor formation process with the existing thin film transistor manufacturing process. The rugged surface structure is formed as part of the standard fabrication sequence using photolithography and etching techniques that are already employed for producing TFTs. This merging approach increases capacitor surface area without adding separate complex manufacturing steps, thus maintaining stored charge while avoiding increased manufacturing complexity.
Solution Approach 2:
The patent employs self-aligned formation methods where the rugged surface structure is created through standard photolithography and etching processes that automatically align with existing transistor structures. The process uses the existing mask patterns and deposition techniques to form the capacitor's three-dimensional structure, making the system self-sufficient and eliminating the need for additional complex alignment or positioning steps.
3Quantity of substance
If traditional methods are used to increase capacitor surface area, then the stored charge is improved, but the manufacturing process becomes too complex for mass production
Solution Approach 1:
The patent replaces complex mechanical impressing methods with standard photolithography and etching processes. Instead of using mechanical rollers or presses to create rugged surfaces, the invention uses optical patterning and chemical etching to form the three-dimensional capacitor structure. This substitution of mechanical systems with optical and chemical processes simplifies the manufacturing approach and makes it suitable for mass production while maintaining increased capacitor surface area and stored charge.
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 method effectively increases the capacitance of capacitors while maintaining the stored charge, allowing for a higher aperture ratio and improved display quality without the complexity of existing methods, facilitating mass production of liquid crystal display devices.
Implementation Method 1
forming an aluminum metal layer (or an aluminum alloy layer) and a metal protecting layer on the substrate, wherein the aluminum metal layer is located between the metal protecting layer and the transparent substrate; patterning a first pattern on the aluminum metal layer of the TFT area, and a second pattern of the metal protecting layer of the storing capacitor area through a halftone mask
Implementation Method 2
forming an aluminum nitride layer on the patterned aluminum metal layer of the TFT area, and on the patterned metal protecting layer of the storing capacitor area
Data Source
AI summary
A method for manufacturing a substrate of a TFT LCD device is disclosed with following steps: providing a transparent substrate having a thin film transistors area and a storing capacitor area; forming an aluminum metal layer and a metal protecting layer on the substrate; patterning a first pattern on the aluminum metal layer of the TFT area, and a second pattern on the metal protecting layer of the storing capacitor area through a halftone mask; forming an aluminum nitride layer on the patterned metal protecting layer; removing the aluminum nitride layer form a rugged surface; forming patterned gates, patterned sources, and patterned drains over the patterned metal protecting layer of the TFT area, and forming a second metal layer over the rugged surface of the aluminum layer on the storing capacitor area, wherein the second metal layer is electrically connected with the drains; and forming patterned pixel electrodes.