LTPS TFT Substrate Heat Sink Layer for Crystallization Control
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Solution Overview
Problem
The existing Excimer Laser Annealing technology for Low Temperature Poly-silicon TFT substrate manufacturing fails to achieve uniform lattice crystallization and direction, leading to non-uniform display effects due to inconsistent polysilicon crystallization across the substrate.
Innovation Solution
A method involving the placement of a heat sink layer under the amorphous silicon layer before Excimer Laser Annealing, allowing for differential crystallization in drive and display areas, where the drive area forms polysilicon with larger lattice dimensions for higher electron mobility and the display area forms polysilicon with smaller lattice dimensions for uniform current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Excimer Laser Annealing is applied uniformly across the substrate, then the polysilicon crystallization process is simplified, but the lattice uniformity and crystallization direction cannot be effectively controlled, resulting in non-uniform display effects
Solution Approach 1:
The patent applies different thermal conditions to different regions of the substrate by introducing heat sink layers selectively in the display area. This creates local quality differences where the display area experiences controlled heat dissipation for uniform small-grain crystallization, while the drive area maintains higher temperatures for large-grain crystallization with fewer grain boundaries. The heat sink layer material and structure are optimized locally to achieve region-specific crystallization characteristics.
Solution Approach 2:
The substrate is segmented into distinct functional areas (drive area and display area) with different thermal management requirements. The heat sink layer is selectively applied only to the display area, creating segmented thermal zones. This segmentation allows independent optimization of crystallization parameters for each area, resolving the contradiction between process simplicity and precision control.
2Ease of manufacture
If the same polysilicon lattice structure is used in both drive and display areas, then the manufacturing process is simplified, but the different electrical property demands of drive TFT and display TFT cannot be satisfied
Solution Approach 1:
The patent creates local quality differences in polysilicon grain structure through region-specific heat sink layer application. The display area develops fine-grain polysilicon with uniform small lattice dimensions suitable for high-resolution displays, while the drive area develops coarse-grain polysilicon with large lattice dimensions and fewer grain boundaries for high electron mobility in drive TFTs. This local differentiation enables each area to meet its specific electrical performance requirements.
Solution Approach 2:
The patent changes the thermal parameters (heat dissipation rate, cooling speed) in different substrate regions by introducing heat sink layers selectively. This parameter change leads to different nucleation and growth rates during laser annealing, resulting in different grain sizes and lattice structures. The drive area maintains higher temperature for slower cooling and larger grains, while the display area experiences faster cooling for smaller grains, thereby adapting electrical properties to different functional requirements.
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 ensures uniform electron mobility and current distribution across the substrate, enhancing the electrical properties and light uniformity of OLED displays by achieving the desired lattice dimensions for drive and display TFTs.
Implementation Method 1
A method involving the placement of a heat sink layer under the amorphous silicon layer before Excimer Laser Annealing
Implementation Method 2
The Excimer Laser Annealing (ELA) technology is the key skill in the LTPS manufacture process. The skill is to utilize the transient pulses of the laser to irradiate on the surface of the amorphous silicon layer to be melted and recrystallized to form the Low Temperature Poly-silicon
Implementation Method 3
utilize the transient pulses of the laser to irradiate on the surface of the amorphous silicon layer to be melted and recrystallized to form the Low Temperature Poly-silicon
Data Source
AI summary
The present invention provides a manufacture method of a Low Temperature Poly-silicon TFT substrate and a Low Temperature Poly-silicon TFT substrate, in which by locating one heat sink layer under the amorphous silicon layer in advance, the difference of the crystallizations of the polysilicons in the drive area and the display area can exist after implementing an Excimer Laser Annealing process to the amorphous silicon layer, and in the drive area, the polysilicon with the larger lattice dimension is formed to promote the electron mobility; the fractured crystals can be achieved in the crystallization process of the display area to form the polysilicon with the smaller lattice dimension for ensuring the uniformity of the grain boundary and raising the uniformity of the current, and thus, the electrical property demands for the different TFTs can be satisfied to raise the light uniformity of the OLED.