SiC Wafer Separation Layers for Step-Free Facet Processing
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Solution Overview
Problem
The existing methods for producing silicon carbide (SiC) wafers from ingots result in a significant waste of material and inefficiencies due to the difficulty in cutting high-hardness SiC ingots, leading to steps between facet and nonfacet areas during laser processing, which complicates wafer thickness uniformity and reduces production efficiency.
Innovation Solution
A method involving a laser processing apparatus that detects facet areas, sets precise coordinates, and adjusts laser energy and focus to form belt-shaped separation layers within the ingot, ensuring equal depth and condition across both facet and nonfacet areas, allowing for step-free separation and efficient wafer production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a wire saw is used to cut the SiC ingot, then the wafer can be produced, but 70% to 80% of the ingot is discarded causing poor economy
Solution Approach 1:
The invention extracts and removes the problematic facet area from the SiC ingot using laser processing before wafer production. By detecting the facet area and selectively removing it through laser-induced separation layers, the ingot is prepared in advance to prevent subsequent processing issues, thereby reducing material waste and improving production efficiency
Solution Approach 2:
The invention performs preliminary detection and removal of the facet area before the main wafer production process. By detecting the facet area coordinates and creating separation layers in advance, the problematic region is eliminated prior to ingot cutting, preventing material waste and productivity loss during subsequent processing steps
2Productivity
If the SiC ingot is cut by wire saw, then the wafer can be obtained, but considerable time is required causing reduction in productivity
Solution Approach 1:
The invention replaces the mechanical wire saw cutting system with a laser-based processing system. By using laser beams to create separation layers and facilitate ingot separation, the time-consuming mechanical cutting process is eliminated, significantly reducing processing time and improving productivity
Solution Approach 2:
The invention changes the processing parameters by using laser energy instead of mechanical force. By controlling laser beam parameters (energy, focal point position, scanning speed) to create separation layers, the processing time is dramatically reduced compared to traditional mechanical cutting methods
3Manufacturing precision
If laser beam is applied to the SiC ingot without considering facet area, then separation layers can be formed, but steps are formed between facet area and nonfacet area
Solution Approach 1:
The invention applies different laser processing parameters to different areas of the SiC ingot based on local characteristics. By detecting the facet area coordinates and applying higher energy with raised focal point position specifically in the facet area, uniform separation layers are achieved across both facet and nonfacet regions, eliminating step formation
Solution Approach 2:
The invention uses feedback from facet area detection to control laser processing parameters. The detected coordinates of the facet area provide feedback that adjusts the laser energy and focal point position in real-time, ensuring uniform separation layer formation while managing the complexity of the processing operation
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 enables the production of SiC wafers with no steps between facet and nonfacet areas, improving the efficiency and economy of wafer production by ensuring uniform separation layers, thus enhancing productivity and reducing material waste.
Implementation Method 1
applying the laser beam from focusing means included in a laser processing apparatus to the SiC ingot, and relatively moving the SiC ingot and the focal point in an X direction parallel to the X axis, thereby forming a belt-shaped separation layer extending in the X direction inside the SiC ingot, the separation layer being composed of a modified portion where SiC is decomposed into Si and carbon (C)
Implementation Method 2
the separation layer being composed of a modified portion where SiC is decomposed into Si and carbon (C)
Implementation Method 3
a plurality of cracks extending from the modified portion along the c-plane
Data Source
AI summary
A wafer producing method includes a facet area detecting step of detecting a facet area from an upper surface of an SiC ingot, a coordinates setting step of setting the X and Y coordinates of plural points lying on the boundary between the facet area and a nonfacet area in an XY plane, and a feeding step of setting a focal point of a laser beam having a transmission wavelength to SiC inside the SiC ingot at a predetermined depth from the upper surface of the SiC ingot, the predetermined depth corresponding to the thickness of the SiC wafer to be produced, next applying the laser beam from a focusing unit in a laser processing apparatus to the SiC ingot, and relatively moving the SiC ingot and the focal point in an X direction parallel to the X axis in the XY plane, thereby forming a belt-shaped separation layer extending in the X direction inside the SiC ingot.