Laser Segmentation of Hexagonal SiC Ingots for Wafer Production
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Solution Overview
Problem
The existing methods for producing hexagonal single crystal wafers from ingots result in significant waste and economic inefficiency, particularly due to the high hardness of materials like SiC and GaN, which makes cutting and processing difficult, leading to 70-80% of the ingot being discarded.
Innovation Solution
A wafer producing method that uses a laser beam to form modified layers and cracks within the ingot, allowing for the direct separation of wafers without converting the ingot into a cylindrical shape, thereby eliminating the need for wire saw cutting and minimizing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire saw cutting is used to slice the ingot, then wafers can be produced, but 70-80% of the ingot is discarded causing poor economy
Solution Approach 1:
The patent divides the ingot into multiple wafers by forming separation planes at regular intervals using laser beams. The ingot is segmented into individual wafer portions along the growth direction, allowing each wafer to be separated without mechanical cutting. This segmentation approach enables utilization of the entire ingot length, eliminating the 70-80% waste associated with wire saw cutting methods.
Solution Approach 2:
The patent replaces the mechanical wire saw cutting system with a laser-based modification system. Instead of using physical blades to slice through the hard ingot material, laser beams are used to form modified layers and induce cracks that create separation planes. This substitution eliminates the need for mechanical contact and enables more efficient material utilization.
2Manufacturing precision
If the ingot is processed into a cylindrical shape with inclined upper surface to achieve off angle, then wafers with predetermined off angle can be produced, but many unwanted scraps are discarded causing poor economy
Solution Approach 1:
The patent applies laser beam modification locally at specific positions within the ingot to create modified layers and cracks. By controlling the laser focal point and scanning patterns, the modification is concentrated at intended separation planes rather than requiring global reshaping of the ingot. This localized approach preserves the original hexagonal shape while achieving the desired off angle characteristics in the final wafers.
Solution Approach 2:
The patent changes the physical state and properties of the ingot material locally through laser heating and modification. The laser beam alters the thermal and structural parameters of the material at specific locations, creating modified layers with different properties that facilitate crack formation and wafer separation. This parameter change approach achieves the off angle requirement without material removal.
3Ease of manufacture
If wire saw cutting is used on hexagonal single crystal ingot with high Mohs hardness, then cutting can be performed, but productivity is reduced due to difficulty in cutting
Solution Approach 1:
The patent replaces mechanical cutting with laser-based modification. The laser beam directly interacts with the hard ingot material to form modified layers and induce cracks, eliminating the need for mechanical force application. This substitution overcomes the limitations imposed by high Mohs hardness and enables faster processing.
Solution Approach 2:
The laser beam induces phase transitions in the ingot material at the focal point, creating modified layers with altered physical properties. The rapid heating and cooling cycles cause localized phase changes that facilitate crack formation and propagation along desired separation planes. This phase transition mechanism enables efficient separation of hard materials without mechanical cutting.
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 enables the economical production of hexagonal single crystal wafers with predetermined off angles, reducing material waste and improving productivity by avoiding the need for wire saw cutting, thus enhancing economic efficiency.
Implementation Method 1
applying the laser beam to the upper surface as relatively moving the focal point and the ingot, thereby linearly forming a modified layer inside the ingot
Implementation Method 2
first cracks extending from the first modified layer along the c-plane
Data Source
AI summary
A wafer having an off angle α is produced from a hexagonal single crystal ingot having an upper surface, a c-plane exposed to the upper surface, and a c-axis perpendicular to the c-plane. The ingot is supported by a wedge member having a wedge angle α equal to the off angle α, thereby inclining the upper surface of the ingot by the off angle α with respect to a horizontal plane. A modified layer is formed by setting the focal point of a laser beam inside the ingot and next applying it to the upper surface, thereby linearly forming a modified layer inside the ingot and cracks extending from the modified layer along the c-plane. The focal point is moved in the second direction to index the focal point by a predetermined amount.