Laser Defect Wafering with Thermal Stress Separation
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Solution Overview
Problem
Current methods for producing thin wafers, such as those used in microelectronics and photovoltaic technology, result in significant material losses due to kerf loss, leading to high production costs and unsuitable wafers with large thickness variations and curvature issues, which complicate further processing and make them unsuitable for many applications.
Innovation Solution
A method involving the creation of defects within a workpiece using laser beams to form a crack-guiding layer, which generates stresses for controlled separation of wafers without conventional sawing, allowing for precise thickness distribution and reduced material waste by using a receiving layer with locally varying properties and an immersion liquid to optimize defect generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional sawing is used to produce thin wafers, then material loss is significant (kerf loss), but the process is simple and well-established
Solution Approach 1:
The patent replaces the mechanical sawing system with a thermal field system. Laser beams create localized melting zones that generate thermal stresses, causing the wafer to separate from the workpiece without mechanical contact. This substitution eliminates kerf loss while avoiding complex mechanical sawing equipment.
Solution Approach 2:
The method utilizes phase transitions of the polymer layer (glass transition) to control its mechanical properties. By heating the polymer above its glass transition temperature, it becomes compliant and allows stress relaxation. Upon cooling, it solidifies and generates thermal stress that drives crack propagation for wafer separation, enabling kerf-free cutting.
2Loss of substance
If polymer layer methods are used for kerf-free wafering, then material loss is reduced, but thickness variation and curvature increase
Solution Approach 1:
The patent applies local quality by creating spatially varying laser power distribution and processing parameters. The laser beams are selectively applied to different regions of the workpiece based on local requirements, allowing precise control of defect depth and density. This enables uniform thickness control across the wafer while maintaining kerf-free separation.
Solution Approach 2:
The method incorporates feedback control through real-time monitoring of the separation process. Sensors detect the position and progress of crack propagation, and the laser processing parameters are dynamically adjusted to maintain uniform thickness. This closed-loop control compensates for variations in material properties and processing conditions.
3Ease of manufacture
If high laser energy is used for layer decomposition, then separation is achieved, but energy consumption increases
Solution Approach 1:
The patent optimizes laser processing parameters including wavelength, power density, pulse duration, and scanning speed to match the absorption characteristics of the polymer layer. By tuning these parameters, the method achieves efficient energy coupling and localized heating with minimal energy waste, reducing overall energy consumption while maintaining effective separation.
Solution Approach 2:
The method uses pulsed laser operation instead of continuous irradiation. The periodic application of laser energy allows heat diffusion between pulses, preventing excessive energy accumulation and reducing total energy requirements. The pulse frequency and duration are optimized to achieve cumulative heating effect that drives crack propagation with minimal energy input.
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 method enables the cost-effective production of wafers with desired thickness distribution and reduced material waste, minimizing thickness variations and curvature issues, thus improving the quality and suitability of wafers for various applications.
Implementation Method 1
creating defects by means of laser beams from a laser within the workpiece
Implementation Method 2
the light absorption at the interface or in an absorption layer provided for this purpose leads to material decomposition
Implementation Method 3
the polymer layer has a thermal expansion coefficient which is approximately two orders of magnitude higher than that of the workpiece
Implementation Method 4
by utilizing a glass transition, a relatively high modulus of elasticity can be achieved in the polymer layer, so that sufficiently large stresses can be induced in the polymer layer-workpiece layer system by cooling
Implementation Method 5
the defects define at least one crack guide layer, wherein the crack guide layer describes at least one three-dimensional contour
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a method for producing at least one three-dimensional solid layer (4), in particular for use as a wafer, and/or at least one three-dimensional solid (40). The method according to the invention preferably comprises the following steps: providing a workpiece (2) for detaching the solid layers (4) and/or the solids (40), wherein the workpiece (2) has at least one exposed surface, generating defects (34) within the workpiece (2), wherein the defects (34) define at least one crack-conducting layer (8), wherein the crack-conducting layer (8) describes at least one three-dimensional contour, applying or generating a receiving layer (10) on the exposed surface of the workpiece (2), thereby forming a composite structure, tempering the receiving layer to generate stresses within the workpiece (2), wherein the stresses give rise to crack propagation within the workpiece (2), wherein, as a result of the crack propagation, a three-dimensional solid layer (4) or a three-dimensional solid (40) is separated from the workpiece (2) along the crack-conducting layer (8), wherein a surface of the solid layer (4) or of the solid corresponds to the three-dimensional contour of the crack-conducting layer (8).