Laser-Modified SiC Wafer Separation via Ultrasonic Vibration
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Solution Overview
Problem
The existing methods for slicing hexagonal single crystal ingots, such as those made of SiC or GaN, are inefficient due to high material loss and low productivity, particularly when using wire saws, and previous laser-based techniques do not adequately improve productivity due to small laser beam pitch requirements.
Innovation Solution
A wafer producing method that involves setting a laser beam focal point at a predetermined depth within the ingot to form a modified layer parallel to the surface and cracks along the c-plane, with the laser beam scanned at an angle relative to the c-axis, followed by ultrasonic vibration in water to separate the wafer from the ingot, reducing material loss and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wire saw is used to slice the ingot, then the wafer can be produced, but 70 to 80% of the ingot is discarded causing poor economy
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based processing system. The laser beam forms a modified layer and induces cracks along the c-plane without requiring mechanical contact, enabling precise separation with minimal material loss while maintaining high productivity for hexagonal single crystal ingots with high Mohs hardness
Solution Approach 2:
The patent changes the physical state and properties of the ingot material through laser heating. By controlling laser parameters (power, scanning speed, pitch) to create a modified layer at specific depth, the material undergoes thermal transformation that facilitates crack propagation along desired planes, enabling efficient wafer separation with reduced material waste
2Productivity
If wire saw is used to cut the hexagonal single crystal ingot, then the ingot can be sliced, but considerable time is required causing reduction in productivity
Solution Approach 1:
The patent replaces slow mechanical wire saw cutting with rapid laser processing. The laser beam can quickly traverse the ingot surface, forming modified layers and inducing cracks at high speed without the mechanical constraints of wire saw operation, significantly reducing processing time and improving productivity
3Manufacturing precision
If laser beam is scanned with pitch of 1 to 10 μm, then modified layer and cracks are formed at high density, but productivity improvement is not yet sufficient
Solution Approach 1:
The patent applies laser processing with different parameters at different locations and orientations. By scanning the laser beam in directions perpendicular to the c-axis inclination and controlling the pitch relative to crack propagation directions, the method creates optimized crack patterns that achieve sufficient separation quality while allowing larger effective pitch, thereby improving productivity
Solution Approach 2:
The patent introduces directional scanning perpendicular to the c-axis inclination rather than scanning parallel to it. This dimensional change in scanning approach allows the laser to effectively create separation planes with adequate crack density while maintaining larger pitch values, resolving the contradiction between precision and productivity
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 method significantly reduces material waste to about 30% and enhances productivity by forming long cracks along the c-plane, allowing for easier separation of wafers from the ingot using ultrasonic vibration, thus improving the efficiency of wafer production.
Implementation Method 1
applying the laser beam to the ingot as scanning the laser beam on the ingot to thereby form a modified layer and cracks in a separation plane inside the ingot
Implementation Method 2
applying ultrasonic vibration to the ingot, thereby separating the plate-shaped member from the ingot to produce the hexagonal single crystal wafer
Data Source
AI summary
A hexagonal single crystal wafer is produced from a hexagonal single crystal ingot. A separation start point is formed by setting a focal point of a laser beam inside the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to a thickness of the wafer to be produced. The laser beam is applied to the upper surface of the ingot while relatively moving the focal point and the ingot to thereby form a modified layer parallel to the upper surface of the ingot and form cracks extending from the modified layer along a c-plane, thus forming a separation start point. The wafer is separated by immersing the ingot in water and then applying ultrasonic vibration to the ingot, thereby separating a plate-shaped member having a thickness corresponding to the thickness of the wafer from the ingot.