SiC Substrate Separation via Laser-Induced Crack Propagation
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Solution Overview
Problem
The existing methods for cutting and separating silicon carbide (SiC) substrates are inefficient, leading to high material wastage and damage during the separation process, as they require small laser beam pitches and lengthy cutting times due to the high hardness of SiC materials.
Innovation Solution
A method involving the use of an adhesive tape with a higher refractive index than air but lower than SiC, combined with a support member, to attach to the SiC substrate, where a laser beam forms a modified layer and cracks parallel to the substrate surface, allowing for efficient separation without damage by applying an external force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wire saw is used to cut SiC ingot, then the ingot can be divided into wafers, but 70% to 80% of the ingot is discarded and considerable time is required for cutting
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based processing system. The laser beam forms a modified layer and induces cracks along the separation plane inside the SiC substrate, allowing separation without mechanical contact. This substitution eliminates the need to discard 70-80% of the ingot and significantly reduces cutting time while maintaining separation effectiveness.
Solution Approach 2:
The patent changes the physical state and properties of the SiC substrate by applying laser energy to create a modified layer with different structural characteristics. By controlling laser parameters (power, scanning speed, focal point position), the modified layer and crack propagation are precisely controlled along the desired separation plane, enabling efficient and waste-free cutting.
2Manufacturing precision
If the laser beam pitch is reduced to 1 μm to 10 μm for precise separation, then separation accuracy is improved, but the processing time increases and productivity is reduced
Solution Approach 1:
The patent applies preliminary action by first forming a modified layer through laser processing before inducing crack propagation. The modified layer acts as a pre-prepared separation path that guides crack formation, allowing larger laser pitch (reducing processing time) while maintaining precise separation accuracy. This preliminary modification enables the system to achieve both precision and productivity.
3Manufacturing precision
If both sides of the wafer are polished to mirror finish after cutting, then surface quality is improved, but the overall production efficiency is reduced due to the lengthy process
Solution Approach 1:
The patent replaces mechanical polishing with laser-induced crack separation that inherently produces clean separation surfaces. The laser processing creates a modified layer that facilitates controlled crack propagation along the separation plane, resulting in surfaces with sufficient quality that reduce or eliminate the need for extensive mechanical polishing, thereby improving production efficiency.
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 separation of SiC substrates into two parts in a planar manner without causing damage, improving productivity and reducing material wastage by reinforcing the substrate surfaces and optimizing laser beam penetration and crack propagation.
Implementation Method 1
applying the laser beam to the SiC substrate as scanning the laser beam on the SiC substrate to thereby form a modified layer and cracks in a separation plane inside the SiC substrate
Implementation Method 2
attaching a transparent adhesive tape to the first surface of the SiC substrate... the refractive index of the adhesive tape is higher than the refractive index of air and lower than the refractive index of the SiC substrate
Data Source
AI summary
Disclosed herein is an SiC substrate separating method for separating an SiC substrate into at least two parts in a planar manner. The SiC substrate separating method includes an adhesive tape attaching step of attaching a transparent adhesive tape to a first surface of the SiC substrate, a support member attaching step of attaching a support member to a second, opposite surface of the SiC substrate, and a separation start point forming step of setting the focal point of a laser beam at a predetermined depth from the adhesive tape and next applying the laser beam to the adhesive tape while relatively moving the focal point and the SiC substrate to thereby form a modified layer parallel to the first surface of the SiC substrate and cracks propagating from the modified layer, thus forming a separation start point.