SiC Laser Processing Chuck Table with Porous Glass Frame
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Solution Overview
Problem
Laser processing methods for silicon carbide (SiC) wafers and ingots often damage chuck tables due to the transmission or reflection of laser beams, and the detection of crystal orientation flats is obscured by metal frames, leading to unclear contrasts and alignment errors.
Innovation Solution
A laser processing apparatus with a chuck table featuring a porous glass plate and a glass frame that transmits laser beams and illuminating light, preventing damage and enhancing orientation detection by maintaining clear contrasts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is applied to process an SiC wafer up to its outer peripheral edge portion, then the processing completeness is improved, but the chuck table may be damaged by the laser beam if it overruns or is transmitted through the SiC wafer
Solution Approach 1:
The patent introduces a beam stopper as an intermediary component positioned between the laser beam path and the chuck table. This beam stopper intercepts and absorbs the laser beam before it can reach the chuck table, thereby protecting the chuck table from laser-induced damage while allowing the laser to fully process the SiC wafer edge without restriction
Solution Approach 2:
The beam stopper is designed as a sacrificial component that absorbs laser energy and can be easily replaced. Rather than protecting the expensive chuck table with complex shielding mechanisms, a simple, replaceable beam stopper is used to absorb the harmful laser energy, embodying the principle of using a cheap, disposable component to protect valuable equipment
2Strength
If a metal frame is used for the chuck table, then the structural strength is improved, but the contrast between the orientation flat and the frame becomes unclear, making it impossible to detect the orientation flat
Solution Approach 1:
The patent applies different material properties to different parts of the chuck table: the frame maintains metal construction for structural strength, while the surface area contacting the SiC wafer is made of a light-absorbing material with a different reflectivity characteristic. This local differentiation in material properties creates sufficient optical contrast between the orientation flat and the frame, enabling accurate detection by the camera unit while preserving the overall structural integrity of the metal frame
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 solution effectively prevents chuck table damage from laser beams and improves the accuracy of crystal orientation detection, reducing errors and enabling precise laser processing of SiC wafers and ingots.
Implementation Method 1
a glass frame made of a non-porous material and having a recess defined therein for receiving the porous material fitted therein... The glass frame transmits therethrough illuminating light emitted by the camera unit
Implementation Method 2
a negative pressure transfer path for transferring a negative pressure to the porous material fitted in the recess
Data Source
AI summary
A laser processing apparatus includes: a chuck table for holding a single-crystal SiC ingot on a holding surface thereof; a laser beam applying unit for applying a laser beam to the single-crystal SiC ingot held on the holding surface of the chuck table; and a camera unit configured to capture an image of the single-crystal SiC ingot held on the holding surface of the chuck table. The chuck table includes a porous material making up the holding surface and a glass frame made of a non-porous material and having a recess defined therein and receiving the porous material fitted therein, and a negative pressure transfer path for transferring a negative pressure to the porous material fitted in the recess.