Vertical LED Metal Support Layer Wafer Warping
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Solution Overview
Problem
Conventional LEDs manufactured on sapphire substrates face issues with heat dissipation due to low thermal conductivity, reduced light emitting region due to electrode formation, and difficulties in wafer separation and chip fabrication, leading to device defects and decreased yield.
Innovation Solution
A vertical LED structure is fabricated using a metal support layer formed by electrolytic plating, comprising a combination of soft and hard metals to enhance mechanical strength and thermal conductivity, eliminating the need for high-temperature processes and preventing wafer warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a sapphire substrate is used for LED fabrication, then the LED structure can be formed, but heat dissipation is poor due to low thermal conductivity
Solution Approach 1:
The patent removes the sapphire substrate from the final LED structure through laser lift-off technology. The sapphire substrate is used only temporarily during fabrication, then extracted and removed, leaving only the GaN layer and metal support structure that provide superior thermal conductivity for heat dissipation.
Solution Approach 2:
The patent changes the thermal conductivity parameter by replacing the sapphire substrate with a metal support structure having high thermal conductivity. This parameter change directly addresses the heat dissipation issue while maintaining structural integrity.
2Ease of manufacture
If mesa-etching is performed to form electrodes, then electrodes can be created, but the light emitting region is reduced
Solution Approach 1:
Instead of removing semiconductor material through mesa-etching to form electrodes, the patent inverts the approach by forming electrodes on the back surface of the GaN layer. This eliminates the need to remove active layer material, preserving the light emitting region while still enabling electrode formation.
3Ease of manufacture
If sapphire substrate is used during dicing and breaking, then chip separation can be performed, but device fabrication yield decreases due to hardness and non-uniform cleavage
Solution Approach 1:
The patent extracts and removes the sapphire substrate before the dicing and breaking processes using laser lift-off technology. This eliminates the problems associated with sapphire's hardness and non-uniform cleavage, allowing for high-yield chip separation while maintaining the temporary utility of sapphire during earlier fabrication steps.
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 solution effectively reduces device defects, improves mechanical strength, and simplifies the fabrication process by allowing for stress-free separation and enhanced heat dissipation without high-temperature processes.
Implementation Method 1
a metal support layer is formed by electrolytic plating on an upper surface of the light emitting structure
Implementation Method 2
a laser beam is irradiated to separate the sapphire substrate from the GaN layer
Data Source
Figure 1~2a
Figure 2b~2c
Figure 2d~2e
AI summary
A vertical structure light emitting diode (LED) and a fabricating method thereof is disclosed, wherein a metal support layer is formed on an upper surface of a light emitting structure by way of electrolytic plating method in which no high temperature process is required to obviate occurrence of defects on the devices, and the metal support layer containing a soft metal and a hard metal is formed on the light emitting structure to prevent occurrence of warping of a wafer to increase the mechanical strength and to improve reliability.