Stress-Alleviation Layer for GaN LED Structures
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Solution Overview
Problem
The manufacturing of light emitting diodes (LEDs) on sapphire substrates often results in crystal defects and stress damage due to thermal expansion and lattice constant differences, which can lead to cracking and damage during the dicing process.
Innovation Solution
Incorporating a stress-alleviation layer on the substrate, which is selectively deposited and patterned to form regions and islands that reduce residual stress during epitaxial growth and dicing, allowing for the use of selective epitaxy and potentially increasing light power emission through additional reflective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN film is grown on sapphire substrate, then LED structure is formed, but crystal defects and cracks occur due to thermal expansion and lattice constant differences
Solution Approach 1:
The patent introduces stress-alleviation regions that partition the continuous GaN film into separate regions, allowing stress to be managed locally rather than accumulating across the entire structure. This segmentation prevents crack propagation and reduces stress damage during dicing operations.
Solution Approach 2:
The stress-alleviation regions act as intermediary elements between the GaN film and the substrate, absorbing and redistributing thermal expansion stresses. These regions serve as a buffer zone that protects the LED structure from harmful stress concentrations during manufacturing processes.
2Productivity
If multiple LEDs are formed on single sapphire substrate and then diced, then manufacturing efficiency is improved, but stress exposure during dicing causes cracking and breakage
Solution Approach 1:
The stress-alleviation regions create natural segmentation between multiple LED structures on the same substrate. This pre-segmentation allows for easier and safer dicing operations, as the stress pathways are already controlled and separated, reducing the risk of crack propagation during the cutting process.
Solution Approach 2:
The stress-alleviation regions are incorporated into the structure before the dicing process, providing预先 cushioning against stress concentrations that would otherwise occur during cutting. This proactive stress management protects the LEDs from damage during subsequent manufacturing steps.
3Reliability
If stress-alleviation regions are introduced, then residual stress is reduced and stress damage is avoided, but device structure becomes more complex
Solution Approach 1:
The stress-alleviation regions are strategically placed only in specific locations where stress concentration is most problematic, rather than uniformly throughout the entire structure. This localized approach provides stress relief where needed while maintaining the simplicity of the overall LED design and minimizing additional complexity.
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 stress-alleviation layer effectively mitigates stress damage during epitaxial growth and dicing, enhancing the structural integrity and light output of LEDs by reducing crystal defects and improving the manufacturing process efficiency.
Implementation Method 1
a stress-alleviation layer that reduces residual stress and avoids stress damage during epitaxial growth and dicing processes
Implementation Method 2
Heteroepitaxial layers are disposed on the substrate at least in the open regions therein, forming an LED structure
Implementation Method 3
a reflective buffer layer, or an additional reflective layer, may be used, thereby increasing the light power emitted from the non-reflective side of the LED
Data Source
AI summary
A light emitting diodes (LEDs) is presented. The LED includes a stress-alleviation layer on a substrate. Open regions and stress-alleviation layer regions are formed on the substrate. Epitaxial layers are disposed on the substrate, at least in the open regions therein, thereby forming an LED structure. The substrate is diced through at least a first portion of the stress-alleviation regions, thereby forming the plurality of LEDs.