Poly Silicon TFT Crystallization for AMOLED Uniformity
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Solution Overview
Problem
Current AMOLED manufacturing methods face challenges in achieving high yield and uniformity due to discrepancies in poly silicon layer crystal grain characteristics, leading to mura issues and increased complexity in multi-crystallization processes.
Innovation Solution
A single laser crystallization process is used to form poly silicon layers with different crystal grain sizes on separate areas of a substrate, employing a heat sink layer to differentiate the crystallization process and meet the distinct electrical requirements of switching and driving TFTs, while also integrating a photo sensor and capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different crystallization processes (ELA and SPC/MIC/MILC) are used to form poly silicon layers with different crystal grain characteristics, then the electrical characteristics of driving TFT and switching TFT can be optimized, but the manufacturing process becomes complicated and time-consuming, reducing productivity
Solution Approach 1:
The patent applies parameter changes by modifying the laser crystallization parameters (energy density, scanning speed, number of scans) to achieve different crystal grain characteristics in poly silicon layers for driving TFT and switching TFT respectively. This allows obtaining the desired electrical characteristics while maintaining a single crystallization process, thus resolving the contradiction between reliability and productivity.
2Reliability
If multiple different crystallization processes are employed to achieve different crystal grain characteristics, then the electrical performance of driving TFT and switching TFT can be optimized, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating poly silicon layers with different crystal grain characteristics in different regions of the substrate through a single laser crystallization process. By controlling laser parameters locally (different energy densities for driving TFT area vs. switching TFT area), the invention achieves the required electrical performance while simplifying the overall process complexity.
3Reliability
If poly silicon layers with different crystal grain characteristics are formed by different crystallization processes, then the mura issue can be addressed, but the manufacturing time and process complexity increase, reducing yield
Solution Approach 1:
The patent resolves the contradiction by changing laser crystallization parameters to achieve different crystal grain sizes - larger crystal grains for driving TFT to reduce mura effect, and smaller crystal grains for switching TFT for high mobility. This single-process approach with parameter optimization simultaneously improves luminance uniformity and manufacturing yield by eliminating multi-process complexity.
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 luminance uniformity, increases photo sensor sensitivity, and reduces capacitor area, thereby improving the aperture ratio of the image display system.
Implementation Method 1
an ELA (Excimer Laser Anneal) is employed to transform an amorphous silicon layer into a poly silicon layer
Implementation Method 2
a laser crystallization process such as ELA (Excimer Laser Anneal)
Implementation Method 3
The driving TFT is positioned on the second area and has a second poly silicon layer and a heat sink layer
Data Source
AI summary
An image display system and manufacturing method are disclosed. According to the present invention, the image display system comprises a substrate, a switching TFT, a driving TFT, a photo sensor and a capacitor. A buffer layer is formed on a substrate. A separation layer is formed in a first area for forming a switching TFT, but no heat sink layer is formed thereon. A heat sink layer is formed on a second area for forming the driving TFT, the photo sensor and the capacitor, and then, the separation layer is formed thereafter. The present invention can form poly silicon layers with different crystal grain sizes on the first area and on the second area in a single laser crystallization process by utilizing the heat sink phenomenon of ELA with or without the heat sink layer. Therefore, the image display system of the present invention can operate with good luminance uniformity.