SiC Wafer Facet Detection via Fluorescence Luminance
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Solution Overview
Problem
The presence of Facet regions in SiC ingots with different crystal structures causes non-uniform peeling layer formation during laser processing, leading to level differences in produced wafers, which affects productivity and efficiency due to the high hardness of SiC ingots and the inefficiency of wire saw cutting methods.
Innovation Solution
A method and apparatus that detect Facet regions by fluorescence luminance unique to SiC, setting coordinates for the boundary between Facet and non-Facet regions, and adjust laser processing conditions to form uniform peeling layers by varying the energy and position of the laser beam based on these coordinates, ensuring uniformity in wafer production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire saw cutting is used to cut SiC ingot, then wafer can be produced from SiC ingot, but productivity is poor and unit cost is high due to long processing time
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser-based processing system. The laser beam forms a peeling layer within the SiC ingot by irradiating at a specific wavelength that is absorbed by the material, enabling non-contact, high-speed processing that eliminates the time-consuming mechanical cutting operation while improving productivity
Solution Approach 2:
The laser processing induces phase transitions in the SiC material by heating it to form a peeling layer. The laser energy causes localized melting and decomposition of SiC into Si and C, creating a weakened layer that allows for easy separation and wafer production, thereby dramatically reducing processing time
2Productivity
If laser beam is used to form peeling layer in SiC ingot, then productivity is improved, but level difference occurs between Facet region and non-Facet region due to different energy absorption rates
Solution Approach 1:
The patent applies local quality by detecting the Facet region and non-Facet region through fluorescence luminance differences, then adjusting laser processing parameters (energy, focus position, scanning speed) specifically for each region. This localized parameter adjustment ensures uniform peeling layer formation despite the different optical properties of the two regions
Solution Approach 2:
The system uses fluorescence luminance detection as feedback to identify region boundaries between Facet and non-Facet areas. This real-time detection information feeds back to the laser control system, which dynamically adjusts processing parameters to maintain uniform peeling layer quality across the entire ingot surface
3Manufacturing precision
If fluorescence luminance detection is used to identify Facet region, then peeling layer uniformity can be controlled, but device complexity increases due to additional detection system
Solution Approach 1:
The fluorescence detection system serves multiple functions: it identifies Facet regions, determines region boundaries, provides feedback for laser parameter adjustment, and enables real-time process control. This multi-functionality justifies the added device complexity by consolidating several control needs into a single integrated detection system
Solution Approach 2:
The fluorescence luminance acts as an intermediary signal that translates the physical difference between Facet and non-Facet regions into detectable information. This intermediary mechanism enables the control system to indirectly sense and respond to regional variations without requiring direct physical measurement of the material properties
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 allows for the production of wafers without level differences between Facet and non-Facet regions, improving the efficiency and quality of SiC wafer production by controlling laser processing conditions based on detected region boundaries.
Implementation Method 1
a fluorescence luminance detecting step of detecting fluorescence luminance unique to SiC by irradiating the SiC ingot with exciting light having a predetermined wavelength from a top surface of the SiC ingot
Implementation Method 2
forming a peeling layer in which SiC is separated into Si and C and a crack extends along the c-plane, by positioning a focusing point formed by condensing a laser beam having a wavelength transmissible through SiC
Implementation Method 3
irradiating a SiC ingot with a laser beam; positioning a focusing point formed by condensing a laser beam having a wavelength transmissible through SiC
Data Source
AI summary
A method of detecting a Facet region includes: a fluorescence luminance detecting step of detecting fluorescence luminance unique to SiC by irradiating a SiC ingot with exciting light having a predetermined wavelength from a top surface of the SiC ingot; and a coordinate setting step of setting a region in which the fluorescence luminance is equal to or higher than a predetermined value in the fluorescence luminance detecting step as a non-Facet region, setting a region in which the fluorescence luminance is lower than the predetermined value in the fluorescence luminance detecting step as a Facet region, and setting coordinates of a boundary between the Facet region and the non-Facet region.