Semiconductor Wafer Laser Peeling With Overlapping Multi-Scan Cracks
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Solution Overview
Problem
Existing laser slicing methods for silicon carbide wafers suffer from issues such as burrs at the laser scanning end, material loss, and harsh process conditions, particularly with pulse lasers requiring precise alignment and synchronization of short and long pulse widths, which hinder large-scale industrial application.
Innovation Solution
A method involving multiple laser scans with controlled scanning paths, point spacing, and laser parameters to form stable modified points and cracks, reducing material loss and eliminating burrs, suitable for large-scale industrial use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If back-and-forth laser scanning is employed to avoid burrs at the laser scanning end, then material loss is reduced to some extent, but the modified layer gradually rises at the laser scan end, still requiring significant grinding or thinning (material loss up to 30%)
Solution Approach 1:
The patent applies periodic action by implementing multiple repeated laser scans (at least two scans) over the same scanning path. Each scan forms modified points that overlap with previous scans, creating a cumulative effect that stabilizes the modified layer position and eliminates the gradual rising phenomenon observed in single-pass or back-and-forth scanning methods.
2Manufacturing precision
If pulse lasers with short and long pulse widths are used for articulated scanning, then modified points and cracks can be formed, but the process conditions become harsh and alignment precision requirements increase
Solution Approach 1:
The patent extracts the complex requirement of using multiple pulse widths by eliminating this need entirely. The invention achieves effective modified point formation and crack generation using a single pulse width laser through multiple scans, thereby removing the need for complex pulse width switching mechanisms and synchronization systems while maintaining manufacturing precision.
3Ease of manufacture
If multiple laser scans are performed with overlapping modified points to form cracks, then peeling difficulty is reduced, but process time increases
Solution Approach 1:
The patent applies preliminary action by performing multiple laser scans that pre-form modified points and initiate crack development before the actual wafer peeling operation. This preliminary modification of the material structure through overlapping scans creates favorable conditions for easy peeling, reducing the need for forceful separation and subsequent processing time.
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
The method effectively reduces material loss and burrs while ensuring simple process conditions and low peeling difficulty, making it suitable for large-scale industrial applications.
Implementation Method 1
performing n times of laser scans on a predetermined peeling surface inside a crystal ingot on which a pulse laser focuses or below the predetermined peeling surface to form a modified point
Implementation Method 2
forming an overlapping region between the modified points formed by at least two laser scans to form a crack extending transversely along the predetermined peeling surface
Data Source
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AI summary
Disclosed herein is a generation method of a semiconductor wafer, including: setting a count of laser scans, setting a scanning path for each laser scan and a point spacing between two adjacent modified points on the scanning path; determining, based on a predetermined rule for each laser scan, a laser scanning speed and a laser pulse repetition frequency required to achieve the point spacing and determining a corresponding diameter of a modified point, and determining laser pulse energy required to achieve the diameter of the modified point and an offset distance of a laser focal point relative to a predetermined peeling surface; performing n times of the laser scans on the predetermined peeling surface inside a crystal ingot on which a pulse laser focuses or below the predetermined peeling surface to form a modified point on the predetermined peeling surface and forming an overlapping region between the modified points formed by at least two laser scans to form a crack extending transversely along the predetermined peeling surface in the overlapping region; and peeling the crystal ingot along the predetermined peeling surface to obtain a wafer and a remaining ingot.The present invention not only eliminates the wafer edge burrs, but also further reduces the material loss of the modified layer, it has the advantages of simple process conditions, good morphology of the modified layer, and low difficulty of peeling of wafers, and is suitable for large-scale industrial applications.