SiC Ingot Polygonal Shaping for Reduced Cutting Waste
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Solution Overview
Problem
The existing methods for forming silicon carbide (SiC) ingots are inefficient, resulting in significant waste due to large cutting margins and poor production efficiency, as seen in the slicing of cylindrical ingots using wire saws.
Innovation Solution
An SiC ingot forming method involving a holding step, planarization of the end surface, detection of the c-plane using a laser beam, and subsequent grinding to form inclined end surfaces and orientation flats, allowing for efficient formation of the ingot while minimizing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wire saw is used to slice a cylindrical SiC ingot, then wafers can be produced, but the cutting margin is large and around 80% of the SiC ingot is disposed of as cutting swarf, leading to poor production efficiency
Solution Approach 1:
The patent changes the geometric parameters of the SiC ingot from a traditional cylindrical shape to a polygonal shape (e.g., hexagonal or octagonal) that matches the wafer layout. This parameter change eliminates the need for large cutting margins, allowing wafers to be produced directly from the polygonal ingot with minimal material waste, thereby improving production efficiency and reducing cutting swarf
Solution Approach 2:
The patent applies the reverse of this principle by replacing the curved cylindrical shape with a polygonal shape having flat faces and sharp edges. The polygonal geometry is specifically designed to accommodate the circular wafer patterns, eliminating the curved cutting margins that would otherwise be wasted in cylindrical ingots
2Manufacturing precision
If the end surface of the primitive SiC ingot is planarized by grinding, then subsequent processing can be performed, but time is consumed in the planarization step
Solution Approach 1:
The patent performs preliminary action by forming the polygonal shape and planarizing the end surfaces during the crystal growth process itself, rather than as a separate post-growth step. The ingot is grown directly into its final polygonal form with flat end surfaces, eliminating the need for subsequent planarization grinding and reducing total processing time while maintaining precision
3Measurement precision
If a laser beam is applied to form a modified layer for c-plane detection, then the c-plane can be detected, but energy is consumed and processing time is added
Solution Approach 1:
The patent merges the c-plane detection function with the existing laser beam processing step used for wafer separation. The same laser beam that creates the modified layer for exfoliation also serves to detect the c-plane orientation by analyzing the crack propagation pattern, thereby eliminating the need for separate detection equipment and reducing overall energy consumption
Solution Approach 2:
The laser beam processing step is designed to serve multiple functions simultaneously: it creates the modified layer for wafer separation, detects the c-plane orientation through crack analysis, and provides alignment information for subsequent processing. This multi-functionality reduces the need for separate dedicated devices and minimizes total energy consumption
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 efficient formation of SiC ingots by reducing the amount of blank material discarded, improving production efficiency and precision in the process.
Implementation Method 1
a laser beam of such a wavelength as to be transmitted through SiC is applied to the SiC ingot, with a focal point of the laser beam positioned at a depth corresponding to the thickness of the wafer to be formed, to form a modified layer in which SiC is separated into silicon (Si) and carbon (C) and a crack extends along a c-plane
Implementation Method 2
a planarization step of grinding an end surface of the primitive SiC ingot held by the chuck table, to planarize the end surface
Data Source
AI summary
An SiC ingot forming method includes: a holding step of holding by a chuck table a cut section of a primitive SiC ingot cut from an SiC ingot growth base; a planarization step of grinding an end surface of the primitive SiC ingot held by the chuck table, to planarize the end surface; a c-plane detection step of detecting a c-plane of the primitive SiC ingot from the planarized end surface; a first end surface forming step of grinding the planarized end surface, to form a first end surface inclined at an off angle relative to the c-plane; and a second end surface forming step of holding the first end surface by the chuck table and grinding the cut section of the primitive SiC ingot in parallel to the first end surface, to form a second end surface.