Wafer Splitting via Defined Stress Distribution
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Solution Overview
Problem
Current methods for producing wafers result in significant material loss and irregularities, such as curvature and thickness fluctuations, due to undesired oscillations and stress peaks during the splitting process, making them unsuitable for many applications.
Innovation Solution
Introducing defined stress distributions within the layer system using a carrier unit with a stabilization layer and a receiving layer, where the stabilization layer has a smaller thermal expansion coefficient than the receiving layer, to control the fracture propagation and achieve uniform thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a polymer layer with high thermal expansion coefficient is used to generate stresses for wafer separation, then the wafer can be separated from the workpiece, but undesired oscillations occur during fracture propagation leading to thickness fluctuations
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the polymer layer to be closer to that of the workpiece material, reducing the stress differential that causes oscillations during fracture propagation. This parameter optimization maintains wafer separation capability while improving thickness uniformity by minimizing excessive stress fluctuations.
Solution Approach 2:
The patent introduces a stress distribution layer with spatially varying properties to create a predefined stress distribution across the workpiece. This local quality variation ensures more uniform stress application during cooling, preventing localized oscillations and improving overall fracture uniformity while maintaining separation efficiency.
2Productivity
If cooling is used to induce stress for wafer cleavage, then the wafer can be separated from the workpiece, but local stress peaks arise that can cause polymer and/or wafer breaking
Solution Approach 1:
The patent modifies the thermal expansion coefficient of the polymer layer to better match the workpiece material, which reduces the magnitude of thermal stresses generated during cooling. This parameter change maintains the stress-induced separation mechanism while preventing excessive stress peaks that would cause wafer or polymer failure.
Solution Approach 2:
The patent introduces a stress distribution layer that pre-distributes stress uniformly across the workpiece before cleavage occurs. This preliminary stress distribution prevents localized stress concentration and peak formation during cooling, protecting both the polymer layer and wafer from breaking while maintaining separation effectiveness.
3Manufacturing precision
If conventional sawing is used for wafer production, then wafers can be produced with controlled thickness, but significant material loss occurs as kerf loss
Solution Approach 1:
The patent replaces the mechanical sawing process with a stress-induced fracture mechanism. By applying thermal stress through a polymer layer with matched expansion coefficient, the workpiece fractures along desired planes without requiring physical removal of material, thereby eliminating kerf loss while maintaining thickness control through stress distribution management.
4Productivity
If a polymer layer is applied to generate stress for splitting, then the wafer can be separated from the workpiece, but the wafer curves strongly in the direction of the polymer layer making further processing difficult
Solution Approach 1:
The patent optimizes the thermal expansion coefficient of the polymer layer to closely match the workpiece material, which reduces the differential thermal stress that causes warping. This parameter adjustment maintains the stress-induced separation mechanism while minimizing curvature development, thereby improving wafer flatness and ease of subsequent processing.
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 significantly reduces thickness fluctuations, allows for more controlled cleavage, and improves the quality of wafers by guiding the fracture progression, resulting in wafers with lower total thickness variations and more uniform spatial thickness distribution.
Implementation Method 1
the stabilization layer has a smaller thermal expansion coefficient than the receiving layer, to control the fracture propagation
Data Source
Figure 1a~1b
Figure 1c~1e
Figure 2a~2f
AI summary
The present invention relates to a method for producing solid layers, in particular for use as wafers. The method comprises the steps of: providing a workpiece (4) for detaching the solid layers, wherein the workpiece (4) has at least one exposed surface; producing and/or providing a support unit for receiving at least one solid layer, wherein the support unit has a receiving layer (2) for retaining the solid layer; and applying the receiving layer (2) to the exposed surface of the workpiece (4) to form a composite structure.Generating a predefined stress distribution (14) within the workpiece (4) to influence, in particular to define, a splitting profile when splitting the solid layer from the workpiece (4) and splitting the solid layer from the workpiece (4) along a plane extending within the workpiece (4) according to the splitting profile influenced by the predefined stress distribution (14).