SiC Wafer Separation via Laser-Induced Modified Layers
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Solution Overview
Problem
The existing methods for producing SiC wafers from single crystal ingots are inefficient due to high discarding of ingot material and low productivity, particularly because the ingots are hard to cut and require extensive time, leading to economic and productivity issues.
Innovation Solution
A wafer producing method that forms a separation surface inside the ingot with a combination of modified layers and connection layers using laser processing, allowing for efficient separation of the ingot into wafers by creating cracks and connection points, thereby reducing material waste and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire saw cutting is used to slice the SiC ingot, then the wafer can be produced, but 70% to 80% of the ingot is discarded and considerable time is required for cutting
Solution Approach 1:
The ingot is divided into multiple wafers through laser-induced modified layers and cracks at regular intervals, allowing sequential separation of thin wafer portions without discarding the bulk material. Each modified layer acts as a separation plane for producing individual wafers.
Solution Approach 2:
The laser processing creates modified layers and cracks in advance within the ingot structure, preparing separation planes before the actual wafer production. This preliminary structuring enables efficient subsequent separation and reduces both material waste and processing time.
2Productivity
If wire saw cutting is used to slice the SiC ingot, then the wafer can be produced, but considerable time is required for cutting due to high hardness
Solution Approach 1:
The mechanical wire saw cutting process is replaced with laser beam processing that creates modified layers and cracks through optical and thermal effects. This substitution eliminates the time-consuming mechanical cutting of hard SiC material while achieving the same wafer separation function.
Solution Approach 2:
The laser processing parameters (wavelength, pulse duration, power density) are optimized to efficiently create modified layers in SiC. By changing the physical state and structural properties of the material through controlled laser parameters, the separation process becomes much faster than mechanical cutting.
3Manufacturing precision
If modified layers are densely formed with a pitch of approximately 10 μm, then the separation surface can be formed, but productivity is reduced
Solution Approach 1:
Multiple functions are combined into a single laser processing step: creating modified layers, generating cracks, and forming connection layers all occur simultaneously through one laser beam pass. This merging of operations maintains separation surface quality while dramatically improving productivity compared to sequential processing.
Solution Approach 2:
The laser beam continuously moves through the ingot creating a continuous separation surface with modified layers and cracks. This continuous processing action eliminates the need for repeated positioning and processing steps, maintaining precision while enhancing production speed.
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 efficient production of SiC wafers with reduced ingot discard, enhancing productivity by allowing easier separation along the formed separation surface, composed of modified layers and connection layers, thus improving the overall efficiency of the wafer production process.
Implementation Method 1
setting a first focal point of a laser beam having a transmission wavelength to SiC at the predetermined depth from the first surface, and next applying the laser beam to the ingot as relatively moving the ingot and the first focal point in the first direction
Implementation Method 2
applying the laser beam to the SiC ingot as scanning the laser beam on the ingot to thereby form modified layers in a separation plane previously set inside the ingot, and next breaking the ingot along the separation plane where the modified layers are formed
Data Source
AI summary
A wafer producing method for producing an SiC wafer from a single crystal SiC ingot. The wafer producing method includes a separation surface forming step of forming a separation surface composed of modified layers, cracks, and connection layers inside the ingot and a wafer separating step of separating a part of the ingot along the separation surface as an interface to thereby produce the wafer. The separation surface forming step includes a modified layer forming step of forming the modified layers and the cracks extending from the modified layers along a c-plane, and a connection layer forming step of forming the connection layers each connecting the cracks formed adjacent to each other in the thickness direction of the ingot.