LED Substrate Surface Treatment for Laser Dicing and Light Extraction
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Solution Overview
Problem
The existing methods for dicing wafers to produce light-emitting diodes are inefficient, leading to high costs and reduced light-emitting efficiency due to traditional laser ablation or melting techniques that cause surface damage and internal reflection, limiting the extraction of emitted light.
Innovation Solution
A method involving a substrate with semiconductor layers and a laser beam that penetrates through a treated surface to cut the substrate, creating a flatter surface for improved light extraction efficiency, using a transparent substrate that can be penetrated by a laser beam to focus internally and reduce total internal reflection, and a reflective layer to enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional laser ablation or melting techniques are used to cut the wafer, then the wafer can be divided into individual LEDs, but surface damage and internal reflection are generated that reduce light extraction efficiency
Solution Approach 1:
The substrate surface is treated in advance before laser cutting to create a roughened surface layer. This preliminary action modifies the surface properties so that when laser cutting occurs, the harmful effects of surface damage and internal reflection are reduced, allowing efficient laser penetration and cutting while maintaining light extraction efficiency
Solution Approach 2:
The roughened surface, which initially might seem to scatter light harmfully, is actually converted into a beneficial feature that reduces total internal reflection at the substrate-semiconductor interface. The roughness creates multiple reflection paths that allow more light to escape, transforming what could be a harmful scattering effect into a beneficial light extraction enhancement
2Object-affected harmful factors
If the substrate surface is left rough, then light extraction efficiency is improved, but laser beam penetration and focusing are hindered
Solution Approach 1:
The substrate surface is treated to create different local qualities: a roughened surface layer that enhances light extraction, and a deeper region that remains relatively smooth to allow laser beam penetration and focusing. This local differentiation resolves the contradiction by providing both roughness benefits at the surface and smoothness benefits at the penetration depth
Solution Approach 2:
The surface treatment is performed in advance to create a controlled roughness profile that optimizes both light extraction and laser cutting. By pre-modifying the surface structure, the subsequent laser cutting process can proceed with high precision while the roughened surface simultaneously improves light extraction efficiency
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 enhances light extraction efficiency by reducing surface roughness and internal reflection, increasing the production efficiency and cost-effectiveness of light-emitting diodes while maintaining the structural integrity of the semiconductor layers.
Implementation Method 1
the laser ablates or melts the wafer from the wafer's surface to the wafer's interior
Implementation Method 2
reducing surface roughness and internal reflection
Data Source
AI summary
A method of manufacturing a light-emitting diode comprises the steps of providing a substrate comprising an upper surface and a bottom surface opposite to the upper surface; providing a semiconductor stack layer on the upper surface, wherein the semiconductor stack layer comprises a first type semiconductor layer having a first surface, a light-emitting layer on the first type semiconductor layer for emitting light, and a second type semiconductor layer on the light-emitting layer; treating the first surface to form a second surface, wherein the second surface is flatter than the first surface; and providing a laser beam through the second surface to cut the substrate.