Laser Peeling of SiC Substrates Using Split Beam Intensity Control
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Solution Overview
Problem
The challenge lies in stably forming a processed layer for peeled substrates made of crystalline materials like silicon carbide, sapphire, or gallium nitride using laser processing, as conventional methods often result in cracks along the crystal orientation, making it difficult to achieve stable separation.
Innovation Solution
A method involving a laser light focusing step using a diffractive optical element to split laser beams into multiple beams of varying intensities, which are focused at specific depths within the substrate to form a processed layer, minimizing crack formation by controlling the intensity distribution and beam arrangement, and a subsequent positioning step for substrate separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser processing is used to form a processed layer in crystalline substrates (SiC, sapphire, gallium nitride), then substrate separation can be achieved, but cracks occur along the crystal orientation making the process unstable
Solution Approach 1:
The laser beam is divided into multiple beams (e.g., three beams) that process different regions of the substrate simultaneously. By segmenting the processing into multiple zones with different laser intensities, the method prevents uniform crack propagation along crystal orientations while maintaining stable processed layer formation across the entire substrate surface.
Solution Approach 2:
Different regions of the substrate are subjected to different laser beam intensities. The patent applies high-intensity laser beams to certain areas and low-intensity laser beams to other areas, creating locally optimized processing conditions that prevent crack formation while ensuring stable processed layer formation in each specific region.
2Ease of manufacture
If conventional laser processing is used on hard materials like silicon carbide, then substrate cutting is attempted, but the hardness of the material makes wire saw cutting and back grinding difficult
Solution Approach 1:
The patent replaces mechanical cutting methods (wire saw cutting) and mechanical grinding (back grinding) with laser-based processed layer formation. By using laser energy to create a processed layer that facilitates separation, the method eliminates the need for mechanical contact with the hard substrate, thereby solving the difficulties associated with cutting and thinning extremely hard materials like silicon carbide and sapphire.
3Stability of the object's composition
If multiple laser beams of equal intensity are used for processing, then uniform processed layer formation is attempted, but this causes cracks to propagate uniformly along crystal orientations
Solution Approach 1:
The patent intentionally creates asymmetric laser beam intensity distribution by using multiple laser beams with different intensities (e.g., high-intensity beams in certain regions and low-intensity beams in other regions). This asymmetric approach prevents uniform crack propagation along crystal orientations while still achieving stable processed layer formation through the combined effect of different intensity zones.
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 allows for the stable formation of processed layers with minimized crack occurrence, enabling efficient separation of peeled substrates while maintaining substrate integrity, and further enhances surface finish through alkali etching.
Implementation Method 1
by using a diffractive optical element configured to split the laser light from the laser light source into a plurality of split laser beams
Implementation Method 2
laser light focusing step of projecting laser light from a laser light source for pulse irradiation through a laser light condenser toward a surface of the substrate and focusing the laser light at a predetermined depth from the surface of the substrate within the substrate
Implementation Method 3
a substrate processing step of forming a processed layer in a substrate made of a crystal substrate, the step including: a laser light focusing step of projecting laser light from a laser light source for pulse irradiation
Data Source
AI summary
A method for manufacturing a peeled substrate has a laser condensing step for focusing laser light at a prescribed depth from the surface of a substrate and a positioning step for moving and positioning a laser condenser relative to the substrate, the method involving forming a processed layer in the substrate. The laser condensing step includes a laser light adjustment step in which a diffraction optical element is used to branch the laser light into a plurality of branched laser beams, and at least one of the branched laser beams is branched such that the intensity thereof differs from the other branched laser beams. The processed layer is elongated using the branched laser beam having a relatively high intensity among the plurality of branched laser beams to process the substrate, and the elongation of the processed layer is restrained using the branched laser beams having a relatively low intensity.