Spot Laser Scanning for Uniform Poly-Silicon Crystal Alignment
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Solution Overview
Problem
Existing laser irradiation methods for forming poly-silicon struggle with achieving high-quality crystal alignment and uniformity, particularly in the formation of thin film transistors for display apparatuses, due to limitations in incident angle, divergence angle, and tilt angle of the laser beam, which affect the crystallization process and alignment properties of poly-silicon grains.
Innovation Solution
A laser irradiation method and apparatus that scans a laser beam in a specific pattern across a substrate, with controlled incident, divergence, and tilt angles, using a spot laser beam and a rotatable scanner, to form poly-silicon by crystallizing amorphous silicon, ensuring the angles satisfy the equation θy [mrad] < 9.33×θ [deg] and maintaining a converging angle of 30 mrad or less, to achieve optimal crystal alignment and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser irradiation methods are used with standard incident angles, then the processing speed and productivity are maintained, but the crystal alignment and uniformity of poly-silicon are insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the incident angle of the laser beam to a specific range (0° < θ ≤ 7.5°) and controlling the divergence angle (θy) and tilt angle (φ) to satisfy the equation θy[mrad] < 9.33×θ[deg]. These parameter adjustments improve crystal alignment and uniformity while maintaining processing efficiency through precise angular control.
2Manufacturing precision
If the laser beam parameters are adjusted to improve crystal quality, then the manufacturing complexity increases, but the product quality improves
Solution Approach 1:
The patent simplifies the control complexity by establishing a clear mathematical relationship (θy[mrad] < 9.33×θ[deg]) between the divergence angle and incident angle, providing a straightforward control criterion that reduces the complexity of parameter adjustment while ensuring high crystal quality.
3Manufacturing precision
If a spot laser beam with small diameter is used to achieve high precision, then the irradiation area coverage is reduced, requiring multiple scans
Solution Approach 1:
The patent introduces a second scanning process in addition to the primary scanning, creating a two-dimensional scanning pattern that ensures complete coverage of the substrate. This dimensional approach allows the use of a small-diameter spot laser beam while maintaining high productivity through systematic multi-pass irradiation.
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
The method and apparatus enable the formation of poly-silicon with excellent alignment and uniformity, reducing manufacturing costs and improving the quality of poly-silicon crystals, suitable for use in display and electronic devices, while maintaining a high-frequency solid-state laser process.
Implementation Method 1
The poly-silicon may be formed by crystallizing an amorphous silicon layer by irradiating an excimer laser to the amorphous silicon
Implementation Method 2
irradiating an excimer laser to the amorphous silicon
Data Source
AI summary
A laser irradiation method includes a first scanning wherein a laser beam is scanned in a first region having a width in the X direction and a length in the Y direction by moving a laser irradiation area on the surface of the substrate along the Y direction using a spot laser beam, and a second scanning wherein laser beam is scanned in a second region having a width in the X direction and a length in the Y direction by moving a laser irradiation area on the surface of the substrate along the Y direction using the spot laser beam. A center of the second region is spaced apart from a center of the first region in the X direction.