SiC Wafer Separation via Laser-Induced Cracks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing SiC wafers from single crystal SiC ingots are inefficient due to high discarding of ingot material and low productivity, particularly because the ingots are hard to cut and require extensive time, leading to economic and productivity issues.
Innovation Solution
An SiC wafer producing method that uses a pulsed laser beam to form modified portions and cracks within the ingot, creating a separation layer for efficient wafer separation, where the laser beam is applied at a predetermined depth with specific energy levels and focal point positioning to minimize material waste and maximize wafer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wire saw is used to cut the SiC ingot, then the wafer can be separated from the ingot, but the cutting time is excessively long and productivity is reduced due to the high hardness of SiC
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser beam processing system. The laser beam forms modified portions and induces cracks within the SiC ingot without mechanical contact, dramatically reducing cutting time and improving productivity while avoiding the limitations of mechanical cutting due to SiC's high hardness.
Solution Approach 2:
The patent changes the processing parameters by using a pulsed laser beam with specific energy density and pulse width to create modified portions in the SiC ingot. By controlling the laser parameters (energy per pulse, pulse repetition frequency, scanning speed), the process achieves efficient separation without mechanical cutting, resolving the productivity-time contradiction.
2Manufacturing precision
If both sides of the wafer are polished to a mirror finish after cutting, then the surface quality is improved, but 70% to 80% of the ingot is discarded causing poor economy
Solution Approach 1:
The patent performs preliminary action by forming modified portions and inducing cracks at the desired separation depth before actual separation. This allows the ingot to be separated cleanly at the predetermined depth with minimal waste, eliminating the need to discard 70-80% of the ingot while still achieving the required wafer thickness and quality.
Solution Approach 2:
The laser-based modified portion formation and crack induction replace traditional mechanical cutting and polishing processes. This substitution enables precise separation at the desired depth with minimal material removal, dramatically reducing ingot waste while maintaining wafer surface quality through controlled crack propagation rather than aggressive mechanical removal.
3Manufacturing precision
If the modified layers are densely formed with a pitch of approximately 10 μm, then the separation layer is sufficiently formed, but the productivity is reduced
Solution Approach 1:
The patent merges two functions into one integrated process: forming modified portions and inducing cracks simultaneously through the same laser beam application. This combination eliminates the need for separate dense modified layer formation, achieving effective separation layers with lower density (reduced pitch) while maintaining separation quality and improving productivity.
Solution Approach 2:
The patent optimizes the laser processing parameters including pulse energy, pulse repetition frequency, and scanning speed to achieve effective crack formation at reduced pitch intervals. By adjusting these parameters, the process forms sufficient separation layers with pitch greater than 10 μm, thereby improving productivity while maintaining manufacturing precision.
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 significantly reduces ingot material waste and enhances productivity by allowing for efficient separation of SiC wafers along the formed separation layer, improving the overall efficiency of wafer production.
Implementation Method 1
setting a focal point of a pulsed laser beam having a transmission wavelength to single crystal SiC inside the SiC ingot at a predetermined depth from an end surface... and next applying the pulsed laser beam to the SiC ingot, thereby forming a small circular modified portion on the c-plane at the predetermined depth, the modified portion being a region where SiC has been decomposed into Si and C
Data Source
AI summary
An SiC wafer producing method includes setting a focal point of a pulsed laser beam to a single crystal SiC inside an ingot at a predetermined depth from an end surface of the ingot, the predetermined depth corresponding to the thickness of the wafer to be produced. The pulsed laser beam is applied to the ingot, thereby forming a small circular modified portion on a c-plane present in the ingot at the predetermined depth, in which the modified portion is a region where SiC has been decomposed into Si and C. A separation layer is formed for separating the wafer from the ingot, the separation layer being composed of a plurality of continuous modified portions and a plurality of cracks isotropically formed on the c-plane so as to extend from each modified portion.