Polycrystalline Silicon Grain Control via Cylindrical Micro-Lens
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Solution Overview
Problem
Conventional methods for crystallizing amorphous silicon to polycrystalline silicon using CW lasers face challenges in adjusting the size and location of crystal grains, leading to limitations in forming polycrystalline silicon thin films with consistent directionality and size, particularly in large-area processes and maintaining high electrical properties.
Innovation Solution
A method involving the use of a cylindrical micro-lens on an amorphous silicon thin film, illuminated with a CW laser beam, which varies the beam intensity and directionality to control the crystallization process, allowing for the formation of polycrystalline silicon with consistent grain size and direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a CW laser is used to crystallize amorphous silicon to form polycrystalline silicon, then the process cost and complexity are reduced compared to excimer laser or SLS methods, but the ability to adjust and control crystal grain size and location is insufficient
Solution Approach 1:
A cylindrical micro-lens array is introduced as an intermediary component between the CW laser and the amorphous silicon substrate. The micro-lens array focuses and shapes the laser beam to create controlled melting zones, enabling precise control over crystal grain nucleation and growth without requiring complex laser systems or masks
Solution Approach 2:
The laser beam is divided into multiple focused spots by the cylindrical micro-lens array, creating segmented heating zones across the substrate. This segmentation allows independent control of crystal grain formation in different regions, enabling precise adjustment of grain size and location while maintaining a simple overall process
2Device complexity
If conventional CW laser crystallization is used, then installation and maintenance costs are lower and the process is simpler, but the directionality and size consistency of crystal grains cannot be effectively controlled
Solution Approach 1:
The cylindrical micro-lens array creates localized heating zones with specific geometric characteristics on the substrate surface. Each micro-lens focuses the laser beam to create a controlled melting pattern that promotes directional crystal grain growth, ensuring consistent grain orientation and size in each local region while maintaining overall process simplicity
Solution Approach 2:
The micro-lens array pre-shapes and positions the laser energy distribution before it reaches the substrate, creating predetermined nucleation sites and growth patterns. This preliminary structuring of the laser beam ensures that crystal grains form with the desired directionality and size consistency from the outset, without requiring complex real-time control systems
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 results in polycrystalline silicon thin films with improved grain directionality and reduced grain boundaries, enhancing electrical properties and overcoming the limitations of existing CW laser-based methods, such as increased grain size and reduced defects, while also simplifying the process and reducing costs.
Implementation Method 1
illuminating a CW laser beam on the amorphous silicon thin film
Implementation Method 2
forming a cylindrical micro-lens on the amorphous silicon thin film
Implementation Method 3
inducing a phase transformation through the heat treatment of amorphous silicon disposed on a substrate
Implementation Method 4
polycrystalline silicon with a structurally and electrically good thin-film property may be obtained when the amorphous silicon is crystallized while being fused and then cooled
Data Source
AI summary
Disclosed are a polycrystalline silicon and a crystallization method thereof according to an exemplary embodiment of the present invention. The polycrystalline silicon comprises: an insulating substrate; and an optical portion formed on the insulating substrate for receiving a CW laser beam and varying the intensity of the beam in order of strength-weakness, strength-weakness, and strength-weakness on one dimension, so that an amorphous silicon thin film is crystallized. Therefore, the present invention can form a good polycrystalline silicon thin film by growing crystal grains with a constant direction and size, when an amorphous silicon thin film disposed on an insulating film such as a glass substrate is crystallized to a polycrystalline silicon thin film.