Laser Wafer Separation for Hexagonal SiC Ingots
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Solution Overview
Problem
The existing methods for slicing hexagonal single crystal ingots, such as SiC and GaN, are inefficient due to high material loss and prolonged processing times, especially when using wire saws, which results in poor productivity and economic waste.
Innovation Solution
A wafer producing method that involves setting the focal point of a laser beam inside the ingot at a predetermined depth to form a modified layer parallel to the surface and cracks along the c-plane, with the laser beam scanned in a specific direction perpendicular to the c-axis inclination, allowing for sequential indexing of focal points to create overlapping cracks for efficient separation.
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 system. The laser beam forms a modified layer inside the ingot at a predetermined depth, creating a separation plane without mechanical contact. This substitution eliminates the need for extensive material removal and enables precise depth control, significantly reducing ingot waste while maintaining high productivity.
Solution Approach 2:
The patent changes the physical state and properties of the ingot material by creating a modified layer through laser heating. By controlling the laser parameters (power, scanning speed, focal depth), the material undergoes localized thermal modification that creates a distinct separation plane. This parameter change allows for precise depth control and minimal material waste compared to mechanical cutting.
2Productivity
If wire saw is used to cut the hexagonal single crystal ingot, then the wafer can be sliced, but considerable time is required reducing productivity
Solution Approach 1:
The patent replaces the slow mechanical wire saw cutting process with a rapid laser-based modified layer formation process. The laser can quickly scan and create the separation plane at controlled depth without the mechanical constraints of wire saw speed, significantly reducing processing time while increasing productivity.
Solution Approach 2:
The patent performs preliminary action by forming the modified layer at the exact predetermined depth before any separation occurs. This pre-positioning of the separation plane eliminates the need for gradual mechanical cutting, allowing for rapid and precise wafer separation that improves productivity.
3Manufacturing precision
If laser beam is scanned with pitch of 1 to 10 μm, then modified layer and cracks are formed at very high density, but the improvement in productivity is not yet sufficient
Solution Approach 1:
The patent introduces a new dimension of control by scanning the laser beam in multiple directions (first direction for modified layer formation, second direction perpendicular to it for indexing). This multi-dimensional scanning approach allows for efficient crack propagation along the c-plane while maintaining productivity, overcoming the limitation of single-direction scanning with its small pitch requirement.
Solution Approach 2:
The patent segments the laser scanning process into two distinct phases: first scanning in one direction to form the modified layer, then indexing and scanning in a perpendicular direction to create the separation plane. This segmentation allows each scanning phase to be optimized independently, achieving both 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 and improves productivity by allowing for efficient separation of hexagonal single crystal wafers from ingots, with only about 30% of the ingot being discarded, compared to the 70-80% loss in traditional methods.
Implementation Method 1
applying the laser beam to the first surface as relatively moving the focal point and the ingot to thereby form a modified layer parallel to the first surface
Implementation Method 2
form a modified layer parallel to the first surface and cracks extending from the modified layer along the c-plane
Data Source
AI summary
A wafer producing method produces a hexagonal single crystal wafer from a hexagonal single crystal ingot. The method includes a separation start point forming step of setting the focal point of a laser beam to the inside of the ingot at a predetermined depth from the upper surface of the ingot, which depth corresponds to the thickness of the wafer to be produced, and next applying the laser beam 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 cracks extending from the modified layer, thus forming a separation start point. The separation start point forming step includes an indexing step of relatively moving the focal point in a direction of formation of an off angle to thereby index the focal point by a predetermined index amount.