LED DBR Structure for Low-Loss Light Extraction and Laser Dicing
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Solution Overview
Problem
Existing LED manufacturing methods face challenges such as light loss due to undesired absorption by the substrate and reduced surface roughness from laser scribing and stealth dicing processes, which affect the brightness and efficiency of LED chips.
Innovation Solution
Incorporating a distributed Bragg reflector (DBR) structure on the substrate with specific reflectance properties to minimize light absorption and maximize laser beam reflection during dicing, allowing for controlled laser scribing and stealth dicing without damaging the semiconductor layered structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser scribing is performed to form trenches extending from the surface to near the substrate-epitaxial structure interface, then light extraction efficiency is improved, but the substrate may undesiredly absorb light causing light loss
Solution Approach 1:
A DBR structure is formed on the substrate surface before the laser scribing process. This preliminary action creates a protective layer that reflects laser beams during dicing, preventing the laser from being absorbed by the substrate and causing unwanted heating or damage, while still allowing the scribing process to proceed effectively
2Manufacturing precision
If stealth dicing is performed with multiple laser scans focused at depths not near the epitaxial structure, then dicing precision is achieved, but surface roughness of the substrate is greatly reduced
Solution Approach 1:
The DBR structure acts as an intermediary layer between the laser beam and the substrate during stealth dicing. It enables precise laser focusing at required depths for clean dicing while protecting the substrate surface from excessive laser exposure that would cause roughening, thus mediating between the conflicting requirements of dicing precision and surface quality
3Manufacturing precision
If the laser beam is focused at depths not near the epitaxial structure during stealth dicing, then dicing accuracy is improved, but the number of laser scans increases reducing surface roughness
Solution Approach 1:
The DBR structure replaces the need for multiple deep-focused laser scans by providing a reflective surface that enhances laser interaction efficiency. This substitution allows for more effective dicing with fewer scans, reducing the time required while maintaining or improving dicing accuracy
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 DBR structure ensures minimal light loss by reflecting the emitted light and effectively guiding the laser beam for dicing, improving the surface roughness and light extraction efficiency of the LEDs.
Implementation Method 1
The DBR structure has a reflectance of not greater than 30% for light having a first wavelength, and a reflectance of not smaller than 50% for a laser beam having a second wavelength
Data Source
AI summary
A light-emitting diode includes a substrate, a distributed Bragg reflector (DBR) structure and a semiconductor layered structure. The DBR structure is disposed on the substrate. The semiconductor layered structure is disposed on the DBR structure opposite to the substrate, and is configured to emit a light having a first wavelength. The DBR structure has a reflectance of not greater than 30% for the light having the first wavelength, and a reflectance of not smaller than 50% for a laser beam having a second wavelength that is different from the first wavelength.