Laser Beam Path Conversion for Uniform Large-Area Crystallization
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Solution Overview
Problem
Existing laser crystallization methods struggle to uniformly irradiate a laser beam over large-sized areas, which is crucial for forming polycrystalline silicon in thin film transistors of large-scale display devices like LCDs and OLEDs, especially as glass substrates increase in size.
Innovation Solution
A laser crystallization apparatus is designed with a path conversion unit that converts laser beams into a linear shape using monolithic incident and emission windows and reflection units, ensuring uniform irradiation across a large area by employing multiple path conversion units and optical elements like lenses, mirrors, and heat sinks to maintain beam intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional laser beam irradiation method is used, then the laser beam can be generated, but the beam intensity is not uniform across large-sized areas
Solution Approach 1:
The patent divides the irradiation area into multiple zones by introducing a light blocking unit that creates segmented laser beams. The light blocking unit is positioned at a specific location to block portions of the laser beam, creating multiple distinct irradiation regions on the substrate. This segmentation allows for better control and uniformity of laser beam intensity across large areas by preventing beam overlap and intensity concentration in specific regions.
2Area of stationary object
If the glass substrate size is increased for large-scale display devices, then the display device scale is improved, but the uniformity of laser beam irradiation deteriorates
Solution Approach 1:
The patent introduces a light blocking unit as an intermediary element between the laser beam source and the substrate. This light blocking unit acts as a mediator to distribute and regulate the laser beam intensity across the large substrate area. By strategically positioning the light blocking unit, the system achieves uniform irradiation across extended areas without requiring changes to the substrate size or laser source characteristics.
3Power
If the laser beam is focused to increase intensity, then the crystallization effect is improved, but the beam becomes concentrated in a small area rather than covering large areas uniformly
Solution Approach 1:
The patent applies segmentation by using a light blocking unit to divide the focused laser beam into multiple segments. Instead of allowing the beam to concentrate in a single small area, the light blocking unit creates multiple separated beam paths that cover a larger overall area. This maintains sufficient power density in each segment for effective crystallization while expanding the total irradiation coverage area uniformly across the substrate.
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 apparatus achieves uniform laser beam irradiation across large areas, facilitating consistent polycrystalline silicon formation, thereby enhancing the operational characteristics of display devices.
Implementation Method 1
a first reflection unit disposed at the same side with the incident window, and a second reflection unit disposed at the same side with the emission window
Implementation Method 2
a first heat sink disposed outside the first reflection unit; and a second heat sink disposed outside the second reflection unit
Data Source
AI summary
A laser crystallization apparatus according to an embodiment includes: a light source unit which irradiates a laser beam; and a path conversion unit which converts the laser beam incident from the light source unit into a linear beam having a long axis parallel to a first direction and a short axis parallel to a second direction. The linear beam propagates in a third direction perpendicular to the first direction and the second direction, the path conversion unit includes an incident window extending parallel to a first length direction, an emission window extending parallel to a second direction, a first reflection unit disposed at the same side with the incident window, and a second reflection unit disposed at the same side with the emission window, and the second length direction extends parallel to the first direction in a view of the third direction.