SiC Ingot Laser Peeling Belt Control by Resistance Measurement
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Solution Overview
Problem
The variability in electric resistance values of SiC ingots makes it difficult to form a proper peeling belt during laser processing, leading to inefficiencies in wafer production and high material loss.
Innovation Solution
A method and apparatus that measure the electric resistance value of the SiC ingot end face, adjust the laser beam output accordingly, and use a laser beam to create a belt-shaped peeling belt with cracks extending along the c-plane, while indexing the peeling belts in the Y-axis direction to ensure proper separation and minimize material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire saw cutting is used to cut SiC ingot, then wafer can be obtained, but cutting time is long and productivity is low due to hardness of SiC
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser processing system. The laser beam processes the SiC ingot without mechanical contact, avoiding the limitations of mechanical cutting due to material hardness. This substitution dramatically reduces processing time and increases productivity while maintaining the ability to produce wafers from the ingot.
2Productivity
If wire saw cutting and polishing is used, then wafer can be obtained, but 70% to 80% of the ingot is discarded which is uneconomical
Solution Approach 1:
The patent applies preliminary laser processing to create a peeling belt at the intended wafer separation location before actual cutting. This preliminary action defines the exact cutting path and enables precise separation, allowing the ingot to be processed into maximum number of wafers with minimal material loss. The peeling belt formation guides subsequent processing to utilize the ingot efficiently.
3Productivity
If laser beam is applied to form peeling belt, then cutting efficiency is improved, but proper peeling belt cannot be formed due to variability in electric resistance value of SiC ingot
Solution Approach 1:
The patent introduces a feedback mechanism where the electric resistance value of the SiC ingot is measured before laser processing. Based on this measured value, the laser beam parameters are automatically adjusted to ensure proper peeling belt formation. This feedback loop compensates for material variability and maintains consistent processing quality across different ingots.
Solution Approach 2:
The patent changes the laser beam parameters (such as power, pulse duration, or focal position) based on the measured electric resistance value of the SiC ingot. By dynamically adjusting these parameters to match the specific material properties, the system ensures optimal peeling belt formation despite variations in ingot characteristics, thereby maintaining both productivity and precision.
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 consistent formation of proper peeling belts in SiC ingots, improving productivity and reducing material waste by optimizing the laser processing parameters based on the ingot's resistance value.
Implementation Method 1
a laser beam of such a wavelength as to be transmitted through the SiC ingot is being applied to the SiC ingot with a focal point of the laser beam positioned at a depth corresponding to the thickness of a wafer to be formed
Implementation Method 2
a crack extends along the c-plane from a part where SiC is separated into Si and carbon (C)
Data Source
AI summary
A method of processing a SiC ingot includes a resistance value measuring step of measuring an electric resistance value of an end face of the SiC ingot, a laser beam output adjusting step of adjusting the output of a laser beam according to the electric resistance value measured in the resistance value measuring step, and a peeling belt forming step in which, while a laser beam of such a wavelength as to be transmitted through the SiC ingot is being applied to the SiC ingot with a focal point of the laser beam positioned at a depth corresponding to the thickness of a wafer to be formed, the SiC ingot and the focal point are put into relative processing feeding in an X-axis direction to form a belt-shaped peeling belt in the inside of the SiC ingot.