SiC Wafer Laser Slicing via Modified Layer Formation
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Solution Overview
Problem
The existing methods for producing silicon carbide (SiC) wafers from ingots are inefficient, resulting in high material wastage and reduced productivity due to the difficulty in cutting hard materials like SiC, and the previous laser-based techniques require extensive time and precision to form a stable separation plane.
Innovation Solution
An SiC wafer producing method that sets the focal point of a laser beam inside the ingot at a predetermined depth from the end surface, forming a modified layer parallel to the surface and cracks, using a focusing lens with a numerical aperture of 0.45 to 0.9 and an M2 factor of 5 to 50 to create a large focal spot, allowing for efficient and stable separation of wafers with reduced ingot wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the numerical aperture of the focusing lens is increased to form a good modified layer, then the depth of focus is reduced to 5 μm or less and the focal point diameter is reduced to 1.5 to 3 μm, but the spacing between adjacent focal points must be set to approximately 10 μm which requires much time and results in low productivity
Solution Approach 1:
The patent changes the M2 factor parameter of the laser beam from the conventional near-ideal value (close to 1) to a larger value of 5 to 50. This parameter change allows the use of a focusing lens with numerical aperture of 0.45 to 0.9 to produce a larger focal point diameter (15 to 150 μm) while maintaining an adequate depth of focus, thereby resolving the contradiction between modified layer quality and productivity
Solution Approach 2:
The patent introduces dynamic adjustment capability by allowing the M2 factor to be varied within the range of 5 to 50, enabling optimization of the focal point size according to specific processing requirements while maintaining efficient wafer production
2Productivity
If the numerical aperture of the focusing lens is reduced to increase the focal point diameter, then the depth of focus is increased, but the modified layer may fluctuate in vertical position and it is difficult to form the modified layer in the same plane
Solution Approach 1:
By changing the M2 factor to a specific range (5 to 50), the patent achieves an optimal balance where the focal point diameter is sufficiently large for productivity while the depth of focus remains adequate to maintain modified layer stability in the same plane, preventing vertical position fluctuations
3Ease of manufacture
If wire saw is used to cut the SiC ingot, then the ingot can be sliced into wafers, but 70% to 80% of the ingot is discarded and considerable time is required for cutting, causing reduction in productivity
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based modified layer formation system. The laser creates a modified layer and cracks that serve as a separation plane, eliminating the need for time-consuming mechanical cutting and reducing material waste while maintaining the ability to slice the ingot into wafers
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 improves productivity by forming a good separation start point efficiently and reduces ingot wastage, enabling the production of SiC wafers with enhanced efficiency and stability.
Implementation Method 1
setting the focal point of a laser beam having a transmission wavelength to the SiC ingot inside the SiC ingot at a predetermined depth from the end surface, which depth corresponds to the thickness of the SiC wafer to be produced, and next applying the laser beam to the end surface of the SiC ingot as relatively moving the focal point and the SiC ingot
Implementation Method 2
setting the numerical aperture of a focusing lens for forming the focal point to 0.45 to 0.9 and substantially setting the M2 factor of the laser beam to 5 to 50 to thereby set the diameter of the focal point to 15 to 150 μm
Data Source
AI summary
A SiC wafer is produced from an SiC ingot having an end surface by setting the focal point of a laser beam at a predetermined depth from the end surface. The depth corresponds to the thickness of the SiC wafer to be produced. The laser beam is applied to the end surface of the SiC ingot while relatively moving the focal point and the SiC ingot to thereby form a modified layer parallel to the end surface and cracks extending from the modified layer, thus forming a separation start point. The separation start point is formed by setting the numerical aperture of a focusing lens to form the focal point to 0.45 to 0.9 and substantially setting the M2 factor of the laser beam between 5 and 50 to thereby set the diameter of the focal point to 15 to 150 μm.