Dual Buffer Amorphous Silicon TFT for Flat Panel Displays
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Solution Overview
Problem
Conventional flat panel displays face issues with impurity diffusion, crystallization defects, and light reflection due to separate processes for buffer layer formation, passivation, and black matrix creation, leading to complex fabrication and increased errors.
Innovation Solution
A dual buffer structure using an amorphous silicon layer as both a buffer and anti-diffuse reflection layer, with a hydrogenated amorphous silicon buffer layer and a patterned amorphous silicon layer to simultaneously form the buffer and black matrix, reducing impurity diffusion and light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer is formed to prevent impurity diffusion, then electrical properties of TFT are improved, but the fabrication process becomes more complex
Solution Approach 1:
The patent combines the buffer layer and black matrix into a single integrated structure. The buffer layer is formed with a patterned configuration that simultaneously serves as both a buffer layer (for preventing impurity diffusion) and a black matrix (for light shielding), thereby reducing the number of fabrication steps while maintaining electrical properties of TFT
Solution Approach 2:
The buffer layer is designed to perform multiple functions: it acts as a buffer layer to prevent impurity diffusion from the substrate, and simultaneously functions as a black matrix to block light in non-emission regions. This multi-functionality eliminates the need for separate black matrix formation steps, simplifying the overall fabrication process
2Reliability
If separate processes are used for buffer layer formation, passivation, and black matrix creation, then each function is optimized, but the number of process variables and potential errors increases
Solution Approach 1:
The patent merges the buffer layer formation and black matrix creation into a single integrated process step. By forming the buffer layer with a patterned configuration that simultaneously serves both functions, the number of process variables is reduced and potential errors from multiple separate processes are minimized
3Reliability
If conductive layers are formed in TFT, then electrical functionality is achieved, but external light causes diffuse reflection degrading contrast ratio
Solution Approach 1:
The buffer layer acts as an intermediary structure between the substrate and the semiconductor layer. By forming the buffer layer with a patterned configuration, it serves as both a buffer layer and a black matrix that blocks light reflection from conductive layers, thereby improving contrast ratio while maintaining electrical functionality
Solution Approach 2:
The buffer layer is formed with different configurations in different regions: in emission regions, it allows light transmission, while in non-emission regions, it functions as a black matrix to block light. This local differentiation resolves the conflict between electrical functionality and light reflection control
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 enhances the contrast ratio by reducing light reflections and improves electrical properties of TFTs, simplifying the manufacturing process and reducing errors, thereby improving the overall performance and reliability of flat panel displays.
Implementation Method 1
To prevent or reduce such impurity diffusion, a method of forming a buffer layer on a substrate has been typically used
Implementation Method 2
a passivation method has been used in order to reduce crystallization defects in the polycrystalline silicon layer
Implementation Method 3
The present invention also provides a flat panel display device for enhancing a contrast ratio by reducing reflection of light due to metal electrodes in an emission region
Data Source
AI summary
A TFT having a dual buffer structure, a method of fabricating the same, and a flat panel display having the TFT, and a method of fabricating the same are provided. The TFT includes a first buffer layer formed of an amorphous silicon layer on a substrate, a second buffer layer formed on the first buffer layer. The TFT also includes a semiconductor layer formed on the second buffer layer and a gate electrode formed on the semiconductor layer. The dual buffer structure provides better barrier to impurities diffusing from the substrate, and also acts as a black matrix to reduce unwanted reflections and is a source of hydrogen to passivate other layers.