Display Substrate Channel Layout for Ordered TFT Crystal Grains
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Solution Overview
Problem
The existing methods for forming polysilicon active layers in thin film transistors, such as AMOLED display panels, often result in unordered crystal grains due to the lack of consideration for the relationship between the excimer laser beam scanning direction and current conduction direction, leading to suboptimal display quality and increased visual defects like Mura (brightness non-uniformity).
Innovation Solution
The display substrate design adjusts the channel direction of the driving transistor to align the current conduction direction with the data line and laser scanning direction, using a semiconductor material layer pattern with specific sub-channel and conductive portions to ensure orderly channel crystal grains, thereby improving field mobility and reducing display defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor material layer is formed using conventional LTPS back plate technology, then the thin film transistor achieves high carrier mobility, but the crystal grains become unordered leading to display defects like Mura
Solution Approach 1:
The patent changes the orientation angle parameter of the semiconductor material layer relative to the data line to specific values (0°, 30°, 45°, 60°, or 90°). This parameter adjustment ensures that the crystal growth direction aligns with the data line direction, promoting orderly crystal grain formation while maintaining high carrier mobility through the LTPS process
Solution Approach 2:
The patent introduces asymmetric orientation between the semiconductor material layer and the data line by specifying particular angle relationships. This asymmetric design breaks the random crystal grain orientation caused by conventional symmetric processing, enabling controlled crystal growth that eliminates Mura defects while preserving the high mobility benefits of LTPS
2Ease of manufacture
If the channel direction is not aligned with the data line direction, then the transistor structure is simpler to manufacture, but the crystal grains become disordered reducing field mobility
Solution Approach 1:
The patent modifies the orientation angle parameter to specific discrete values that simultaneously satisfy manufacturing simplicity and performance requirements. By selecting angles of 0°, 30°, 45°, 60°, or 90° relative to the data line, the design maintains straightforward fabrication processes while ensuring optimal crystal grain alignment for high field mobility
3Device complexity
If the excimer laser beam scanning direction is not considered in the design, then the manufacturing process is simpler, but visual defects like Mura increase
Solution Approach 1:
The patent introduces a specific parameter relationship between the semiconductor material layer orientation and the data line direction (0°, 30°, 45°, 60°, or 90°). This parameter specification ensures that crystal grains grow in an orderly manner during excimer laser processing, eliminating Mura defects without significantly increasing process design complexity
Solution Approach 2:
The patent performs preliminary design of the semiconductor material layer orientation before the actual manufacturing process. By pre-establishing the correct angular relationship between the material layer and data line, the design prevents crystal grain disordering during laser processing, thereby preventing Mura defects before they occur
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 field mobility and output current characteristics of the driving current region, reduces visual defects like Mura, and improves the overall quality and yield of the display substrate by ensuring orderly channel crystal grains.
Implementation Method 1
the relationship between the excimer laser beam scanning direction and current conduction direction
Implementation Method 2
result in unordered crystal grains
Data Source
AI summary
A display substrate, a method of forming a display substrate, a display panel and a display device are provided. The display substrate includes a thin film transistor array layer, where a semiconductor material layer pattern of a driving transistor in the thin film transistor array layer includes a first channel portion, and the first channel portion includes a first sub-channel portion and a second sub-channel portion; the semiconductor material layer pattern further includes a first conductive portion, an included angle between a straight line where a current conduction direction of the first sub-channel portion is located and a straight line where an extending direction of a data line in the thin film transistor array layer is located is a first included angle.