Tilted Laser Beam for Uniform Polysilicon Crystallization
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Solution Overview
Problem
Current laser crystallization methods for polycrystalline silicon TFTs in display panels suffer from crystallization defects due to stage ripples and uneven laser beam irradiation, leading to non-crystallization areas and reduced productivity.
Innovation Solution
A laser crystallization apparatus that transforms a rectangular laser beam into a tilted non-rectangular parallelogram beam, irradiated perpendicular to the substrate, with the stage moving only along the X-axis, reducing stage ripples and ensuring consistent beam alignment across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rectangular laser beam is used for crystallization, then the beam can be easily generated and guided, but stage ripples cause uneven irradiation and crystallization defects
Solution Approach 1:
The patent transforms the conventional rectangular laser beam into a tilted non-rectangular parallelogram beam by introducing an asymmetric optical element (prism or tilted lens). This asymmetric beam shape compensates for the stage ripple effects, ensuring uniform energy distribution across the substrate during scanning, thereby eliminating crystallization defects while maintaining ease of beam generation.
Solution Approach 2:
The patent changes the geometric parameters of the laser beam by transforming it from a rectangular cross-section to a tilted non-rectangular parallelogram cross-section. This parameter transformation is achieved through optical elements that modify the beam's shape and orientation, allowing the beam to maintain consistent alignment with the substrate throughout the scanning process and eliminate non-crystallization areas.
2Area of stationary object
If the stage moves along both X-axis and Y-axis directions, then the laser beam can cover the entire substrate area, but stage ripples increase causing more crystallization defects
Solution Approach 1:
The patent introduces a tilt dimension to the laser beam by transforming it into a non-rectangular parallelogram shape with a specific tilt angle. This dimensional change allows the beam to compensate for stage ripple effects in the vertical direction while the stage moves horizontally along the X-axis, enabling full substrate coverage without increasing crystallization defects.
Solution Approach 2:
By using an asymmetric tilted beam shape instead of a symmetric rectangular beam, the patent enables the laser to maintain uniform irradiation across the substrate even when the stage moves along multiple directions. The asymmetric geometry of the beam matches the asymmetric motion pattern, ensuring consistent crystallization quality throughout the scanning area.
3Ease of operation
If the laser beam is irradiated at an angle to the substrate, then beam alignment may be adjusted, but the irradiation is not perpendicular causing uneven crystallization
Solution Approach 1:
The patent uses an asymmetric tilted beam shape that is generated by optical elements such as prisms or tilted lenses. This asymmetric transformation allows the beam to be directed perpendicular to the substrate surface while maintaining a tilted geometric configuration, ensuring uniform energy distribution and consistent crystallization across the entire irradiation area.
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 eliminates non-crystallization areas and improves productivity by maintaining consistent beam alignment from start to end, reducing stage ripples and enhancing the crystallization process for display panels.
Implementation Method 1
a tilt refractive lens configured to transform the laser beam having a cross-sectional area of a rectangle shape into a tilted laser beam having a cross-sectional area of a non-rectangular parallelogram shape
Implementation Method 2
laser crystallization apparatus for reducing crystallization defects
Data Source
AI summary
A laser crystallization apparatus includes a laser generating module configured to generate a laser beam, an optical module configured to guide the laser beam, an annealing chamber comprising a stage on which a target substrate comprising an amorphous thin film formed therein is disposed, the stage being movable along an X-axis direction and a Y-axis direction, and a tilt refractive lens configured to transform the laser beam having a cross-sectional area of a rectangle shape into a tilted laser beam having a cross-sectional area of a non-rectangular parallelogram shape and to irradiate the tilted laser beam perpendicular to the stage.