Laser Marking Refractory Substrates to Prevent Contamination
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Solution Overview
Problem
Forming a highly visible identification mark on refractory material single crystal substrates, such as silicon carbide, gallium nitride, and sapphire, is challenging due to their high melting points and hardness, which leads to issues like contamination and surface scars from residual contaminants in the recessed portions of dot-based marks.
Innovation Solution
A method involving scanning the substrate surface with a laser beam at a first energy density to form grooves, followed by a finishing process at a lower energy density to remove contaminants and smooth the internal surface, ensuring the grooves have a width of at least 50 μm and a depth of 10 μm, and optionally including mechanical polishing and gas phase etching to achieve a smooth surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is used to form an identification mark on a refractory material single crystal substrate, then the identification mark can be formed, but the substrate surface may be contaminated and surface scars may occur due to residual contaminants in the recessed portions
Solution Approach 1:
The identification mark is segmented into multiple independent dots arranged in a matrix pattern, rather than using continuous lines or large recessed areas. This segmentation reduces the total volume where contaminants can accumulate and makes each dot less prone to trapping contaminants during the laser forming process
Solution Approach 2:
The laser beam parameters (energy density, pulse duration, scanning speed) are locally optimized for forming clean dot recessions. The patent specifies using a pulsed laser beam with controlled energy density to melt and evaporate material cleanly, and subsequent cleaning steps are applied specifically to the dot regions to remove any residual contaminants before epitaxial growth
2Illumination intensity
If the identification mark is formed with deep recessed portions, then visibility is improved, but contamination and surface scars increase due to trapped contaminants
Solution Approach 1:
The laser beam energy is carefully controlled to create recessed portions with optimal depth that provides sufficient visibility while minimizing contaminant trapping. The patent specifies using pulsed laser beams with energy densities that melt and evaporate material to form clean recessions without creating excessively deep cavities where contaminants would accumulate
Solution Approach 2:
A cleaning step is performed before epitaxial growth to remove residual contaminants from the recessed portions of the identification mark. This preliminary cleaning action prevents contaminants from being trapped and causing surface scars during subsequent processing
3Ease of manufacture
If a pulsed laser beam is used to form the identification mark, then the mark can be formed on the refractory substrate, but residual contaminants may remain in the recessed portions
Solution Approach 1:
The laser beam scanning continues systematically across the entire substrate surface to form all identification mark dots uniformly. The patent specifies using a pulsed laser beam that scans along the substrate surface in a controlled manner, ensuring consistent formation of clean recessions throughout the identification mark without interrupting the process in a way that would leave residual contaminants
Solution Approach 2:
A cleaning step is performed before epitaxial growth to remove residual contaminants from the recessed portions. This preliminary action ensures the substrate is clean and free of contaminants that could cause surface scars during subsequent processing
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 produces identification marks with excellent visibility and minimal contamination, preventing surface scars and ensuring the substrate remains clean and smooth, even after subsequent processing steps.
Implementation Method 1
a laser beam is usually used. The semiconductor in a region irradiated with a laser beam is melted and evaporated
Implementation Method 2
The semiconductor in a region irradiated with a laser beam is melted and evaporated
Data Source
AI summary
An identification mark formation method for forming an identification mark on a refractory material single crystal substrate that is made of one selected from the group consisting of sapphire, gallium nitride, aluminum nitride, diamond, boron nitride, zinc oxide, gallium oxide, and titanium dioxide is disclosed. The method includes: (a) scanning a principal surface of the refractory material single crystal substrate with a laser beam at a first energy density such that a groove is formed in the principal surface of the refractory material single crystal substrate, thereby forming an identification mark in the principal surface of the refractory material single crystal substrate; and (b) scanning an inside of the groove of the refractory material single crystal substrate with a laser beam at a second energy density that is lower than the first energy density.