SiC Wafer Separation With Relaxed Positive Bow and Low Kerf Loss
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Solution Overview
Problem
Conventional methods for slicing silicon carbide (SiC) wafers, such as wire sawing, result in significant kerf losses, material deformation, and high production costs due to high stress and long processing times, limiting the ability to produce thin wafers efficiently.
Innovation Solution
A method involving laser-assisted separation of SiC wafers from bulk crystalline material, forming subsurface damage patterns that allow for reduced kerf losses and intentional wafer shapes to mitigate deformation and sagging, enabling the production of wafers with a relaxed positive bow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wire sawing is used to slice SiC wafers, then cutting capability is achieved, but kerf losses increase significantly
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based separation system. The laser induces subsurface damage patterns that enable wafer separation through controlled fracturing rather than mechanical removal, dramatically reducing kerf losses from millimeters to micrometers while maintaining cutting capability.
Solution Approach 2:
The patent introduces subsurface damage patterns as an intermediary mechanism between the laser energy and the wafer separation process. These patterns act as pre-formed fracture paths that guide the separation process, enabling precise material release with minimal material loss.
2Productivity
If wire sawing is used to slice SiC wafers, then wafer production is achieved, but processing time increases significantly
Solution Approach 1:
The patent employs periodic pulsed laser irradiation to create subsurface damage patterns. The pulsed nature of the laser allows for efficient energy delivery and heat management, enabling rapid processing while maintaining precision. Multiple wafers can be processed in sequence through the bulk crystal efficiently.
Solution Approach 2:
The laser pre-processes the bulk SiC crystal by creating subsurface damage patterns before actual wafer separation. This preliminary action prepares the material for easy fracturing along predetermined paths, significantly reducing the time required for subsequent wafer release compared to direct mechanical cutting.
3Ease of manufacture
If wire sawing is used to slice SiC wafers, then cutting is achieved, but material deformation and bow increase
Solution Approach 1:
The patent replaces mechanical cutting forces with optical energy delivery. The laser-induced subsurface damage and subsequent stress-free fracturing process avoids the high mechanical stresses of wire sawing that cause wafer bow and deformation, resulting in flatter, more dimensionally stable wafers.
Solution Approach 2:
The patent converts the potentially harmful effect of laser-induced subsurface damage into a beneficial feature. The controlled damage patterns serve as predetermined fracture paths that enable clean wafer release without mechanical stress, transforming what could be a defect into a useful separation mechanism that preserves wafer flatness.
4Ease of manufacture
If wire sawing is used to slice SiC wafers, then wafer separation is achieved, but production costs increase
Solution Approach 1:
The patent replaces expensive mechanical wire sawing with a laser-based system that uses minimal material. The reduction in kerf losses from millimeters to micrometers directly translates to significant material savings, offsetting the cost of laser equipment and operation.
Solution Approach 2:
The patent changes the fundamental parameter of kerf width from the millimeter scale (wire diameter) to the micrometer scale (laser beam width). This parameter change dramatically reduces the volume of material removed during processing, directly reducing production costs associated with material loss.
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 approach reduces kerf losses to less than 250 microns, minimizes material deformation, and enhances processing efficiency, allowing for the production of SiC wafers with improved shape integrity and reduced production costs.
Implementation Method 1
providing at least one laser; introducing laser radiation of the laser into the interior of the bulk crystalline material to a focus point of the laser for modifying the material properties of the bulk crystalline material
Data Source
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Figure 4A~4B
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AI summary
Silicon carbide (SiC) wafers (8A) and related methods are disclosed that include intentional or imposed wafer (8A) shapes that are configured to reduce manufacturing problems associated with deformation, bowing, or sagging of such wafers (8A) due to gravitational forces or from preexisting crystal stress. Intentional or imposed wafer (8A) shapes may comprise SiC wafers (8A) with a relaxed positive bow from silicon faces thereof. In this manner, effects associated with deformation, bowing, or sagging for SiC wafers (8A), and in particular for large area SiC wafers (8A), may be reduced. Related methods for providing SiC wafers (8A) with relaxed positive bow are disclosed that provide reduced kerf losses of bulk crystalline material (70, 90, 92A, 92). Such methods may include laser-assisted separation of SiC (6H) wafers (8A) from bulk crystalline material (70, 90, 92A, 92).