Laser-Cut LED Substrate Cleaning for Light Extraction
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Solution Overview
Problem
Current methods for manufacturing nitride semiconductor light-emitting diodes face challenges in efficiently removing by-products from laser beam cutting, which reduces light extraction efficiency and increases manufacturing costs due to the hardness of sapphire or SiC substrates and the damage caused by dry etching or incomplete removal with wet etching methods.
Innovation Solution
A method involving laser beam cutting of substrates followed by immersion in a chemical solution containing phosphoric and sulfuric acid at controlled temperatures to effectively remove by-products, with protective layers to prevent damage, allowing for efficient cleaning and enhanced light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser beam cutting is used to separate sapphire or SiC substrates, then cutting speed and efficiency are improved, but by-products are generated on the substrate surface reducing light extraction efficiency
Solution Approach 1:
The patent converts the harmful by-products generated by laser cutting into beneficial roughened surfaces. The chemical cleaning solution not only removes the by-products but also creates a rough surface texture that enhances light extraction efficiency through increased light scattering and reduced total internal reflection.
Solution Approach 2:
The patent introduces a chemical cleaning solution as an intermediary substance between the laser cutting process and the final LED product. This intermediary agent (chemical solution) mediates the removal of harmful by-products while simultaneously creating the desired rough surface morphology for improved light extraction.
2Object-generated harmful factors
If dry etching method is used to remove by-products, then by-product removal is achieved, but device damage occurs and product yield is reduced
Solution Approach 1:
The patent replaces the mechanical/physical dry etching process with a chemical cleaning approach. Instead of using physical sputtering or ion bombardment that can damage the device, a chemical solution is used to dissolve and remove by-products gently, preserving the integrity of the LED structure.
Solution Approach 2:
The patent changes the removal mechanism from physical/ mechanical (dry etching) to chemical dissolution. By changing the fundamental parameter of the removal process from kinetic energy bombardment to chemical reaction, the method achieves by-product removal without device damage.
3Object-generated harmful factors
If wet etching with KOH solution is used to remove by-products, then some cleaning is achieved, but complete removal is not accomplished and manufacturing cost increases
Solution Approach 1:
The patent changes the chemical composition parameters of the cleaning solution from KOH-based to a specific acidic solution formulation. This parameter change in chemical composition enables complete removal of the laser-induced by-products that were resistant to KOH-based cleaners.
Solution Approach 2:
The patent optimizes the cleaning solution composition by referencing and improving upon existing wet etching methods. It adopts the liquid-phase chemical cleaning approach but modifies the chemical composition to achieve superior cleaning effectiveness and complete by-product removal.
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 approach enables efficient removal of by-products, improving light extraction efficiency and reducing manufacturing costs by optimizing the cleaning process with controlled temperature and time, while protecting the substrate from damage.
Implementation Method 1
Another separation method involves scribing the wafer by a high energy density laser beam ablating the bonds between atoms of the substrate
Implementation Method 2
removing the by-product by a chemical solution containing an acid under a predetermined cleaning temperature
Data Source
AI summary
A method of manufacturing a light-emitting device comprising the steps of cutting a substrate by a laser beam to form a cavity in the substrate and generate a by-product directly on the substrate by the cutting, and removing the by-product by a chemical solution containing an acid under a predetermined cleaning temperature.