Laser Crystallization Line Beam Shaping for Uniform Polysilicon
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Solution Overview
Problem
Existing laser crystallization methods face challenges in achieving uniform crystallization and high crystallization margin due to the long axis angular distribution of the line beam, which affects the quality of polysilicon formation and subsequently the performance of thin film transistors in display devices.
Innovation Solution
A laser crystallization apparatus comprising multiple laser generators, attenuators, and an optical module that adjusts the energy intensity and direction of laser beams to minimize long axis angular distribution, using inclined attenuation units and a homogenizer to produce a uniform line beam for crystallizing amorphous silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional laser beam is used for crystallization, then the crystallization process can be completed, but the long axis angular distribution of the line beam causes poor crystallization uniformity and reduced crystallization margin
Solution Approach 1:
The laser beam is divided into multiple sub-beams (first line beam, second line beam, third line beam) that are separately controlled and then superimposed. Each sub-beam is generated by separate laser generators and attenuators, allowing independent adjustment of energy intensity and angular distribution. This segmentation enables precise control over the final line beam's properties, resolving the contradiction between crystallization uniformity and crystallization margin by optimizing each sub-beam's contribution.
Solution Approach 2:
Different regions of the line beam are assigned different energy intensities and angular distributions through the use of multiple attenuators (first attenuator, second attenuator, third attenuator) and inclined attenuation units. The first and third line beams have different energy intensities and angular distributions compared to the second line beam, creating local quality variations that optimize both uniformity and crystallization margin across different areas of the crystallization region.
2Manufacturing precision
If the energy intensity of laser beams is not adjusted, then the apparatus structure remains simple, but the long axis angular distribution cannot be minimized and crystallization quality deteriorates
Solution Approach 1:
The attenuators and optical modules serve multiple functions: they adjust energy intensity, control angular distribution, and shape the line beam simultaneously. The inclined attenuation units not only reduce energy intensity but also modify the angular distribution of the laser beams. This multi-functionality reduces the need for separate components, thereby limiting the increase in apparatus complexity while achieving superior crystallization quality.
Solution Approach 2:
The energy intensity parameters of the laser beams are precisely adjusted using attenuators with specific transmission rates (e.g., first attenuator with 70% transmission, second attenuator with 30% transmission). By changing these parameters systematically, the apparatus achieves optimal crystallization quality without requiring fundamentally different or more complex hardware architectures.
3Stability of the object's composition
If multiple laser generators are used to reduce angular distribution, then crystallization margin and uniformity improve, but the energy intensity control becomes more complex
Solution Approach 1:
The system incorporates control units that receive signals from detectors and adjust the energy intensity of each laser beam accordingly. The detector measures the actual energy intensity and angular distribution of the combined line beam, and the control units modify the attenuator settings to achieve the desired crystallization parameters. This feedback mechanism simplifies the overall control by automating the complex adjustments that would otherwise require manual intervention.
Solution Approach 2:
The energy intensity of each laser beam is pre-adjusted using attenuators before the beams are combined. The first attenuator pre-attenuates the first line beam, the second attenuator pre-attenuates the second line beam, and the third attenuator pre-attenuates the third line beam. This preliminary action ensures that when the beams are superimposed, they achieve the optimal energy distribution for crystallization without requiring complex real-time adjustments during the crystallization process.
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 improves crystallization margin and uniformity, resulting in polysilicon crystal particles of uniform size and enhancing the image quality of display devices by reducing beam divergence and asymmetric reflections.
Implementation Method 1
Polysilicon may be formed by depositing amorphous silicon and then crystallizing the amorphous silicon. Amorphous silicon may be crystallized into polysilicon by heating the amorphous silicon in a hot furnace or irradiating the amorphous silicon with a laser.
Implementation Method 2
Amorphous silicon may be crystallized into polysilicon by heating the amorphous silicon in a hot furnace or irradiating the amorphous silicon with a laser.
Data Source
AI summary
A laser crystallization apparatus includes a plurality of laser generators which generate a plurality of laser beams, a plurality of attenuators which adjust energy intensity of the plurality of laser generators, and an optical module which overlap outputs of the plurality of attenuators to output a line beam. A first attenuator of the plurality of attenuators attenuates the energy intensity of the corresponding laser beam, and a second attenuator of the plurality of attenuators maintains the energy intensity of the corresponding laser beam.