TFT Pixel Structures with Bump-Induced Uneven Reflective Layers
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Solution Overview
Problem
Conventional reflective and transflective LCD pixel structures require complex fabrication processes and high costs due to the need for additional mask processes to create a reflective layer with an uneven surface, which complicates the simultaneous fabrication of thin film transistors and reflective layers.
Innovation Solution
A method that simplifies the fabrication process by forming a substrate with active and pixel regions, where a gate and bumps are created, followed by a gate insulation layer, semiconductor layer, source and drain, patterned protection layer, and a reflective layer, using inorganic materials to reduce the number of mask processes and integrate the reflective layer with the transistor fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional fabrication processes are used to create a reflective layer with an uneven surface, then the reflection effect is improved, but the number of mask processes increases to seven, resulting in higher manufacturing costs and lower productivity
Solution Approach 1:
The patent combines the formation of the reflective layer with the formation of the pixel electrode into a single mask process. The reflective layer and pixel electrode are patterned simultaneously using one mask, reducing the total number of mask processes from seven to five. This merging of operations maintains the uneven surface structure for reflection while improving productivity.
Solution Approach 2:
The pixel electrode layer serves dual functions: as the electrical component for controlling liquid crystal and as the reflective layer for light reflection. By making the pixel electrode also function as the reflective layer, the patent eliminates the need for a separate reflective layer fabrication process, thereby reducing mask processes while maintaining both electrical functionality and reflection effect.
2Reliability
If seven mask processes are used to fabricate the pixel structure, then the thin film transistor and reflective layer can be formed, but the manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent merges multiple fabrication steps into fewer mask processes. Specifically, the reflective layer and pixel electrode are formed in the same mask process, and the pixel electrode also serves as the reflective layer. This consolidation reduces the number of mask processes from seven to five, lowering manufacturing costs while maintaining complete fabrication of all necessary components.
Solution Approach 2:
The pixel electrode is designed to perform multiple functions: electrical control of the liquid crystal and light reflection. This multi-functionality allows the elimination of a separate reflective layer, reducing the number of fabrication steps and associated costs while ensuring all functional requirements are met.
3Shape
If organic material is used to form the protection layer as bumps, then the uneven surface for reflection is achieved, but the fabrication process becomes more complex due to different material characteristics
Solution Approach 1:
The patent uses inorganic material for both the protection layer and the reflective layer/pixel electrode. This material homogeneity allows the same fabrication parameters and processes to be used throughout, eliminating the need to switch between organic and inorganic material processes. The uneven surface is still achieved through the bump structure, but the uniform material type simplifies the overall fabrication process.
Data Source
AI summary
A fabricating method of a pixel structure is provided, which uses the original processes of fabricating a thin film transistor to simultaneously fabricate a reflective layer with an uneven surface. In the fabrication process of the thin film transistor, a plurality of bumps are formed under the reflective layer which is to be formed later on. The bumps and a gate of the TFT are formed simultaneously or the bumps and a semiconductor layer of the TFT are formed simultaneously. In addition, by stacking layers on the bumps, the reflective layer formed on the bumps can have good uneven shapes on the surface thereon. Therefore, the fabricating method of a pixel structure has simple processes and low manufacturing costs, and can be used for fabricating a transflective pixel structure or a reflective pixel structure.