Ramp Shaped Laser Beam Crystallization for Polysilicon Grain Growth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for crystallizing polysilicon, such as furnace heating, are inefficient and cannot be used with glass substrates due to temperature limitations, while laser crystallization methods face challenges in achieving uniform crystal growth and high-speed operation required for advanced liquid crystal display devices.
Innovation Solution
A method using a ramp-shaped laser beam for sequential lateral solidification, where the laser beam intensity gradually decreases in the scanning direction to form larger crystal grains, allowing for asymmetric crystallization and reduced crystallization time by using the asymmetrical regions as seeds for further growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If furnace heating is used to crystallize polysilicon, then complete crystallization can be achieved, but the crystallization speed is low and glass substrates are deformed at temperatures higher than 600°C
Solution Approach 1:
The patent replaces the conventional furnace heating method with laser beam irradiation. The laser provides localized energy to induce crystallization without requiring the entire substrate to reach high temperatures, thus avoiding glass substrate deformation while achieving fast crystallization speed through direct energy coupling with the silicon layer.
Solution Approach 2:
The patent uses a ramp-shaped laser beam intensity profile that creates different crystallization conditions across the irradiation area. The intensity gradually decreases from one side to the other, creating a gradient that promotes directional crystal growth and enables complete crystallization at lower peak temperatures compared to uniform heating methods.
2Manufacturing precision
If conventional laser crystallization is used, then crystallization can be achieved at lower temperatures, but the crystal grains are small and uniformity is poor
Solution Approach 1:
The patent employs an asymmetric ramp-shaped laser beam intensity profile where the intensity gradually decreases in the scanning direction. This asymmetric distribution creates a temperature gradient that promotes directional crystal growth from high to low intensity regions, resulting in larger and more uniform crystal grains while maintaining fast crystallization speed.
Solution Approach 2:
The patent changes the laser beam intensity distribution parameter from uniform to ramp-shaped. This parameter modification creates a controlled gradient in energy input that directs crystal growth orientation and size, achieving both large uniform grains and high crystallization speed that cannot be obtained with conventional uniform intensity laser crystallization.
3Manufacturing precision
If multiple laser beam irradiations are performed to form uniform large crystal particles, then crystal quality improves, but the processing time increases
Solution Approach 1:
The ramp-shaped laser beam performs preliminary action by creating an asymmetric temperature distribution that pre-establishes favorable conditions for large crystal grain formation in a single pass. This eliminates the need for multiple irradiation steps, as the gradient structure inherently promotes directional growth that produces uniform large grains immediately.
Solution Approach 2:
The patent achieves continuous crystallization across the entire silicon layer in a single scanning operation. The ramp-shaped intensity profile ensures that as the laser moves, each region receives optimized energy input for crystal growth, maintaining continuous useful action without interruption or repetition, thus reducing processing time while ensuring uniform large grain formation.
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 increases the size of polycrystalline silicon grains, enhances crystallization speed, and reduces the time required for complete substrate crystallization, improving the productivity and operational speed of liquid crystal display devices.
Implementation Method 1
irradiating a high intensity laser on a small region and then cooling it
Implementation Method 2
instantaneously melting an amorphous silicon layer by irradiating a high intensity laser
Implementation Method 3
induces crystallization by instantaneously melting an amorphous silicon layer
Implementation Method 4
laser beam having a ramp shaped cross sectional profile that decreases in a scanning direction
Data Source
AI summary
A crystallization method, includes: forming an amorphous silicon layer on a substrate; forming a first crystallization region by irradiating the amorphous silicon layer with a laser beam having a ramp shaped cross sectional profile that decreases in a scanning direction; and performing a second crystallization by moving a predetermined length in a scanning direction so as to be partially overlapped with the first crystallization region formed by the first crystallization.