Laser Peel-Off Layer Sequencing for Crack-Reduced Substrate Slicing
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Solution Overview
Problem
The existing methods for manufacturing substrates from cylindrical ingots using a wire saw result in low productivity due to large saw kerfs, surface irregularities, and significant material waste during slicing and planarization.
Innovation Solution
A method involving the use of a laser beam with a wavelength transmittable through the ingot material to form peel-off layers in a successive array along the ingot, allowing for the separation of substrates with reduced material waste and increased productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wire saw is used to slice substrates from an ingot, then substrates can be manufactured, but the productivity is low due to large saw kerfs and significant material waste
Solution Approach 1:
The patent replaces the mechanical wire saw slicing process with a laser-based peeling process. The laser beam forms modified regions and cracks within the ingot to create peel-off layers, eliminating the need for mechanical cutting. This substitution reduces the kerf width from approximately 300 μm to nearly zero, dramatically reducing material waste and increasing productivity.
Solution Approach 2:
The patent changes the physical state and properties of the ingot material through laser irradiation. By controlling laser parameters (wavelength, power, scanning speed, focal position), the material undergoes localized modification forming peel-off layers with cracks that enable clean separation. This parameter control allows precise manipulation of the separation process without mechanical contact.
2Manufacturing precision
If a wire saw is used to slice substrates, then substrates can be obtained, but the surfaces have irregularities and require extensive planarization
Solution Approach 1:
The patent replaces mechanical slicing with laser-induced peeling, where the laser forms controlled cracks and modified regions that separate along predetermined planes. This process inherently produces smoother surfaces with fewer irregularities compared to mechanical sawing, reducing the need for subsequent planarization operations.
Solution Approach 2:
The laser process performs preliminary separation by forming peel-off layers and cracks within the ingot before actual substrate extraction. This pre-created separation path ensures that when substrates are removed, their surfaces are already relatively flat and smooth, requiring minimal post-processing.
3Productivity
If peel-off layers are formed in successive areas from one end to the other of the ingot, then substrates can be separated, but large cracks develop in the thicknesswise direction reducing surface quality
Solution Approach 1:
The patent employs periodic action by forming peel-off layers in multiple discrete areas along the ingot length rather than continuously. The laser scans through different regions sequentially, creating separated peel-off zones that prevent stress accumulation. This periodic formation allows stress relief between areas, preventing large through-thickness cracks.
Solution Approach 2:
The patent segments the peel-off layer formation into multiple distinct areas along the ingot. Instead of forming one continuous peel-off layer, the process creates separated zones of modification. This segmentation divides the stress distribution, preventing the development of large cracks that would occur in a continuous single-layer 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
The method effectively reduces material waste and increases productivity by dispersing internal stresses and preventing large cracks in the ingot, resulting in substrates that require less planarization material and have improved surface quality.
Implementation Method 1
a peel-off layer forming step of repeatedly moving the workpiece and a focused spot, the focused spot being positioned within the workpiece, of a laser beam that is applied to the workpiece and has a wavelength transmittable through a material of the workpiece
Implementation Method 2
The modified regions contained in the peel-off layers are regions where the crystal structure of the ingot material is disrupted. Therefore, the modified regions formed in the ingot tend to produce internal stresses in the ingot.
Implementation Method 3
external forces are exerted on the ingot, separating a substrate from the ingot along the peel-off layers that act as separation initiating points
Data Source
AI summary
A peel-off layer is finally formed in an area, i.e., a first inner area or a second inner area, in a workpiece that is closer to the center of the workpiece among a plurality of areas. The workpiece has a cylindrical shape, so that the second inner area is wider than the other areas, e.g., the second outer area, in which the peel-off layers are formed. Consequently, when the peel-off layer is finally formed in the second inner area, the internal stresses in the workpiece are dispersed in a wider range than when the peel-off layer is finally formed in the second outer area. Thus, large cracks thicknesswise of the workpiece are prevented from being developed from modified regions contained in the peel-off layer. Therefore, the amount of workpiece material to be disposed of in subsequent steps is reduced, resulting in increased manufacturing productivity.