Crystal Wafer Slicing Offset to Minimize Defect Wafers
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Solution Overview
Problem
Conventional methods for wafering industrially grown crystals, such as sapphire and silicon carbide, are time-intensive, costly, and result in significant waste due to internal defects, necessitating a more efficient and automated process to reduce defects and increase yield.
Innovation Solution
A method involving 3D scanning to create a digital model of the crystal, recording defect coordinates, measuring crystal axes, and optimizing core extraction and slicing with an offset position to minimize defects, using a system with a scanner, coring device, and wafer slicing machine to automate the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional manual methods are used to determine crystal axes and optimize core distribution, then measurement and decision-making can be performed with simple equipment, but the process becomes time-intensive and costly
Solution Approach 1:
The patent replaces manual mechanical measurement methods with automated optical scanning and image processing systems. The scanner captures 3D images of the crystal, and computer algorithms automatically determine crystal axes and optimize core positions, eliminating time-consuming manual operations while maintaining measurement accuracy.
Solution Approach 2:
The patent creates a digital 3D model (copy) of the crystal from scanned images. This digital replica allows for rapid virtual optimization of core positions and slicing plans without physically manipulating the crystal, significantly reducing the time required for planning while preserving all geometric and orientational information.
2Loss of substance
If conventional slicing methods are used without defect optimization, then the slicing process is simple and rapid, but significant waste occurs due to internal defects in the wafers
Solution Approach 1:
The patent performs preliminary scanning and defect mapping of the crystal before the slicing process. By identifying the locations of internal defects in advance through optical scanning and creating a digital model, the system can pre-optimize core positions and slicing plans to avoid defects, minimizing waste before the actual cutting begins.
Solution Approach 2:
The patent optimizes multiple parameters including crystal axis orientation, core position coordinates, and slicing plane angles to minimize defect inclusion. The computer algorithm calculates optimal parameter combinations that maximize yield by positioning wafer cuts between defect locations while maintaining required crystallographic orientations.
3Productivity
If automated scanning and optimization systems are implemented, then productivity and yield increase, but the device complexity and initial cost increase
Solution Approach 1:
The patent employs a multi-functional integrated system where a single scanning apparatus performs multiple tasks: capturing 3D crystal geometry, identifying internal defects, determining crystal axes orientations, and providing data for optimization calculations. This consolidation reduces overall system complexity compared to having separate dedicated devices for each function.
Solution Approach 2:
The computer-based optimization system automatically processes the scanned crystal data, determines optimal core positions and slicing plans, and generates control instructions for the slicing machine without requiring manual intervention. The system serves itself by using its own captured data to optimize the processing parameters, reducing operational complexity.
Data Source
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AI summary
A method of producing wafers or discs from an industrially grown crystal comprising the steps of: - scanning a crystal (1) in volume and forming a 3D volumetric digital model of the crystal, - recording 3D spatial coordinates of defects (4, 4') detected during said scanning, - measuring one or more crystal axes (C1, C2, C3) provided by a crystalline structure of the crystal, and recording this crystal axis in said 3D model of the crystal, - coring out one or more cores (2) from the crystal (1) in a selected crystal direction which is parallel to one of said crystal axes or at a defined angle with respect to said crystal axis, - slicing the core orthogonally to the selected crystal direction with a wafer slicing machine comprising a slicing tool comprising a plurality of cutting wires or blades spaced at a regular slicing pitch (G) configured to cut wafers of identical thicknesses (S) from the core, - wherein the method includes computing an offset position (O) of the slicing tool along the selected crystal axis configured to have a minimum number of wafers with defects, and - adjusting the position of the slicing tool relative to the core along the selected crystal direction according to the computed offset.