Laser-Defined Crack Paths for Kerf-Free Solid Layer Splitting
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Solution Overview
Problem
Current methods for producing solid-state layers, such as wafers, face challenges including significant material loss, uneven thickness, and difficulty in achieving reproducible thermal contact, leading to fluctuations in wafer thickness and quality, particularly due to kerf loss and complex, costly processes like ion implantation.
Innovation Solution
A method involving the use of a radiation source, like a laser, to generate defects and specify a crack initiation point and path within the solid material, followed by thermal stress application to induce separation, allowing for precise control of crack propagation and even layer production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional sawing is used to produce wafers, then material loss is significant (kerf loss), but the process is simple and well-established
Solution Approach 1:
The patent replaces the conventional mechanical sawing system with a thermal stress-based separation system. A polymer layer is applied to the workpiece, and thermal stresses are induced through controlled heating and cooling cycles. The polymer layer expands and contracts at different rates than the workpiece, generating sufficient stress to separate the wafer without mechanical contact, thereby eliminating kerf loss while avoiding complex mechanical sawing equipment
Solution Approach 2:
The invention exploits differential thermal expansion between the polymer layer and the workpiece. The polymer layer has a thermal expansion coefficient approximately two orders of magnitude higher than the workpiece. By controlling the thermal cycles, the polymer expands and contracts to generate stresses that initiate and propagate cracks along the desired separation plane, enabling kerf-free wafer separation
2Loss of substance
If polymer layer thermal stress method is used to separate wafers, then material loss is reduced, but thickness uniformity deteriorates due to significant thickness variations
Solution Approach 1:
The patent applies preliminary actions to control the fracture propagation process. Before the main separation step, the polymer layer is pre-heated to a temperature above the glass transition temperature to ensure uniform adhesion. During cooling, the thermal stress is applied in a controlled manner to initiate cracks at specific locations. The process includes multiple thermal cycles with controlled heating rates and holding times to ensure uniform stress distribution and consistent crack propagation, thereby improving thickness uniformity while maintaining the kerf-free advantage
3Ease of operation
If polymer layer is used to generate thermal stresses, then wafer separation is achieved, but polymer adhesion causes wafer bending and thickness variations
Solution Approach 1:
The patent employs dynamic control of the polymer layer's mechanical properties through temperature cycling. The polymer is heated above its glass transition temperature during the separation process to maintain flexibility and adhesion, enabling smooth wafer release. After separation, the polymer is cooled below the glass transition temperature to become rigid and maintain its shape. This dynamic property change allows the polymer to adapt to the wafer during separation while preventing excessive bending and thickness variations in the final product
4Manufacturing precision
If ion implantation is used to produce wafers, then wafer quality is improved, but process cost and complexity increase significantly
Solution Approach 1:
The patent replaces the expensive and complex ion implantation process with a simpler, more economical approach using a disposable or reusable polymer layer. The polymer layer serves as a temporary medium to generate the necessary thermal stresses for wafer separation. After use, the polymer can be removed and replaced, avoiding the need for expensive ion guns and complex control systems while still achieving high wafer quality through controlled thermal stress-induced fracture propagation
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 enables the production of solid-state layers with significantly reduced total thickness variation (TTV) and improved uniformity, reducing material waste and production costs while maintaining high accuracy and precision.
Implementation Method 1
generating defects by means of at least one radiation source, in particular a laser, in the internal structure of the solid to define a crack initiation point
Implementation Method 2
the polymer layer exhibits a thermal expansion coefficient approximately two orders of magnitude higher than that of the workpiece. Furthermore, by exploiting a glass transition, a relatively high elastic modulus can be achieved in the polymer layer, so that cooling can induce sufficiently large stresses
Implementation Method 3
thermally applying the receiving layer to generate, in particular mechanically, stresses in the solid, whereby the stresses cause a crack to propagate from the crack initiation point and/or along the crack path in the solid
Data Source
Figure 1a~1e
Figure 2a~2c
Figure 3a~3b
AI summary
The present invention relates to a method for producing solid layers. The method according to the invention preferably comprises the steps of: providing a solid body (2) for splitting off at least one solid layer (4), creating defects by means of at least one radiation source (18), in particular a laser, in the internal structure of the solid body for predetermining a crack-initiating point, starting from which the solid layer (4) is split off from the solid body (2), and/or creating defects by means of at least the radiation source (18), in particular a laser, in the internal structure of the solid body (2) for predetermining a cracking line, along which the solid layer (4) is split off from the solid body (2), arranging a receiving layer (10) for holding the solid layer (4) on the solid body (2), thermally treating the receiving layer (10) for the creation, in particular mechanical creation, of stresses in the solid body (2), wherein the stresses cause a crack to spread from the crack-initiating point and/or along the cracking line in the solid body (2), detaching the solid layer (4) from the solid body (2).