Curved Solid Layer Separation by Laser-Guided Crack Spalling
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Solution Overview
Problem
Conventional wafering and thinning processes for semiconductor materials result in material loss, surface damage, and increased costs due to kerf losses and Wallner line patterns, which require additional polishing and grinding steps.
Innovation Solution
A laser-assisted spalling process that uses laser modifications to define a crack propagation plane with micrometer precision, allowing for the production of curved or bent solid layers by controlling crack guidance and minimizing surface roughness through techniques like Brewster angle irradiation and refractive index matching coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional diamond- or slurry-based wire sawing processes are used for wafering, then material can be separated from the ingot, but material loss due to kerf increases and surface damage occurs requiring additional polishing and grinding steps
Solution Approach 1:
The patent extracts the harmful kerf material removal process and replaces it with a stress-based separation method. By applying external stresses to induce crack propagation along crystal planes, the method separates wafers without mechanical cutting, thereby eliminating kerf loss while maintaining high productivity through direct separation.
Solution Approach 2:
The patent replaces the mechanical wire sawing system with a stress-induced crack propagation system. Instead of using diamond- or slurry-based mechanical cutting, the method applies controlled external stresses to initiate and guide cracks along desired separation planes, substituting mechanical removal with a controlled fracture mechanism that preserves material and reduces surface damage.
2Loss of substance
If spalling processes are used to separate crystalline materials along crystal planes, then material loss is reduced, but Wallner line patterns are created on the surface increasing surface roughness
Solution Approach 1:
The patent applies local quality by creating a stress concentration zone at a specific location (edge or surface) to initiate crack propagation. By controlling where the stress is applied and how it propagates, the method achieves clean separation along crystal planes while minimizing unwanted surface features like Wallner lines, thus reducing surface roughness locally at the separation front.
Solution Approach 2:
The patent performs preliminary action by pre-positioning stress concentration zones or initiating cracks at controlled locations before the actual separation process. This allows the crack to propagate along the desired crystal plane from a predetermined starting point, ensuring clean separation and reducing the formation of Wallner line patterns that increase surface roughness.
3Manufacturing precision
If additional polishing and grinding steps are performed to remove Wallner line patterns, then surface quality is improved, but process costs increase and further damage occurs
Solution Approach 1:
The patent extracts the source of Wallner line formation by modifying the crack initiation and propagation mechanism. By controlling stress application and using appropriate stressors, the method achieves separation with minimal Wallner line formation, thereby eliminating the need for subsequent polishing and grinding steps that would otherwise be required to remove these patterns.
Solution Approach 2:
The patent ensures continuity of useful action by achieving both separation and surface quality improvement in a single integrated process step. The stress-induced crack propagation method simultaneously accomplishes material separation along crystal planes and maintains surface quality by minimizing Wallner line formation, eliminating the need for separate polishing and grinding operations.
4Manufacturing precision
If conventional spalling methods are used, then separation along crystal planes is achieved, but control over wafer thickness and crack propagation location is limited
Solution Approach 1:
The patent implements feedback control by monitoring crack propagation in real-time and adjusting stress application parameters accordingly. By using sensors to detect crack position and propagation rate, the system can dynamically adjust the magnitude and location of applied stresses to maintain precise control over crack path and final wafer thickness, ensuring accurate separation at the desired crystal plane.
Solution Approach 2:
The patent applies dynamics by using adjustable and controllable stressors that can dynamically change their application parameters during the separation process. The stress magnitude, direction, and location can be modified in real-time to guide crack propagation along the desired path and achieve precise wafer thickness control, making the process adaptable to different material properties and separation requirements.
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 process reduces material loss and surface roughness, achieving Ra < 1 µm and Sa < 1 µm, eliminating the need for additional polishing and grinding steps, and enabling efficient production of curved or bent wafers.
Implementation Method 1
generating laser beams (10) by means of a laser irradiation device (8) to generate at least one modification (2) inside the solid (1), wherein the modifications (2) define a crack propagation area (4)
Implementation Method 2
separating the solid layer (14) from the solid (1) as a result of the pressure increase along the crack propagation area (4) by crack propagation
Implementation Method 3
the laser radiation is directed onto the solid (1) at the Brewster angle or with a deviation in the range of -10° to +10° from the Brewster angle
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The present invention relates to a method for separating at least one solid layer (14) from a solid body (1), wherein the modifications (2) define a crack guidance area (4) for guiding a crack to separate a solid component (6), in particular a solid layer, from the solid body (1).Preferably, the present invention comprises at least the following steps: moving the solid (1) relative to a laser application device (8), successively generating laser beams (10) by means of the laser application device (8) to generate at least one modification (2) each, wherein the laser application device (8) is adjusted for defined modification generation depending on at least one parameter, in particular the transmission of the solid at defined locations and for a defined solid depth, wherein inhomogeneities of the solid (1) in the area of the applied surface and/or in the area of the applied volume of the solid (1) are compensated by adjusting the laser application device (8), separating the solid layer (14) from the solid (1).