Monocrystalline Silicon Substrate Peeling for Low-Kerf Wafering
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Solution Overview
Problem
The existing method of manufacturing monocrystalline silicon substrates from ingots using a wire saw results in large saw kerfs, surface irregularities, and low productivity due to significant material wastage.
Innovation Solution
A method involving the formation of peel-off layers in a workpiece of monocrystalline silicon using a laser beam with a wavelength transmittable through the silicon, allowing for the separation of substrates along these layers, thereby increasing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire saw is used to slice substrates from ingots, then substrates can be manufactured, but large saw kerfs result in significant material wastage and low productivity
Solution Approach 1:
The patent replaces the mechanical wire saw slicing process with a laser-based peeling process. A laser beam is used to form peel-off layers within the monocrystalline silicon ingot, which then allow substrates to be separated through peeling rather than mechanical cutting. This substitution eliminates the need for wide saw kerfs, reducing material wastage from approximately 1/3 to minimal amounts, while simultaneously improving productivity through a more efficient separation process
Solution Approach 2:
The patent changes the physical state and structural parameters of the monocrystalline silicon by using laser irradiation to create peel-off layers with specific crystallographic orientations. By controlling the laser parameters (wavelength, power, scanning speed) and the ingot orientation relative to crystal planes, the process creates controlled separation planes that enable clean substrate separation without mechanical contact, thereby reducing both material loss and processing time
2Manufacturing precision
If wire saw slicing is used, then substrates are produced, but surface irregularities and curvature require extensive lapping, etching, and polishing
Solution Approach 1:
The laser peeling process performs the separation action in advance along predetermined crystallographic planes, creating inherently flat and smooth substrate surfaces during the separation process itself. Because the peel-off layers form along specific crystal orientations, the resulting substrate surfaces are naturally flat without the curvature and irregularities produced by mechanical sawing, thereby eliminating or significantly reducing the need for subsequent lapping, etching, and polishing operations
Solution Approach 2:
The patent replaces multiple mechanical finishing processes (lapping, etching, polishing) with a laser-based separation process that inherently produces high-quality surfaces. The laser-induced peel-off mechanism separates substrates along crystallographic planes that provide natural flatness, substituting complex mechanical finishing equipment and multi-step processes with a single laser processing step that achieves both separation and surface finishing simultaneously
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
The method enhances productivity by reducing material wastage and eliminating the need for extensive lapping, etching, and polishing, while ensuring high-quality substrate surfaces.
Implementation Method 1
moving a focused spot, positioned within the workpiece, of a laser beam that is applied to the workpiece and that has a wavelength transmittable through the monocrystalline silicon and the workpiece
Implementation Method 2
forming a peel-off layer in a straight area in the workpiece along the first direction
Data Source
AI summary
After peel-off layers have been formed in a workpiece of monocrystalline silicon such as an ingot, a bare wafer, or a device wafer with use of a laser beam having a wavelength transmittable through monocrystalline silicon, a substrate is separated from the workpiece along the peel-off layers acting as separation initiating points. The process results in increased productivity for the manufacture of substrates, compared with a process of manufacturing substrates from a workpiece with use of a wire saw.