LED Bond Layer Planarization for Void-Free Epitaxial Bonding
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Solution Overview
Problem
Existing light emitting diode (LED) structures face issues with void formation during bonding processes, leading to reduced bonding stability, increased voltage, and decreased efficiency due to Au—Au or Au—In bonding methods.
Innovation Solution
A light emitting diode element is designed with an epitaxial structure, a reflection structure, a first bond layer, and a substrate, where the first bond layer fills vias in the reflection structure and covers a flat zone, ensuring a flat surface for bonding without voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Au—Au bonding or Au—In bonding is adopted to bond the epitaxial structure to a substrate, then the bonding process can be completed, but voids are formed in the bond layer which reduces bonding stability and causes separation of the epitaxial layer from the substrate
Solution Approach 1:
The patent applies preliminary action by forming a flat zone in the reflection structure before the bonding process. This flat zone is created by removing the void-prone curved portion of the reflection structure, thereby preventing void formation during subsequent bonding operations. The flat zone serves as a pre-prepared bonding surface that eliminates the root cause of void formation.
Solution Approach 2:
The patent applies the taking out principle by extracting or removing the curved portion of the reflection structure that causes void formation. By taking out this problematic portion and replacing it with a flat zone, the source of void formation is eliminated while retaining the essential bonding functionality.
2Reliability
If Au—In bonding is used to bond the epitaxial structure, then bonding can be achieved, but the cost increases and production efficiency decreases
Solution Approach 1:
The patent applies this principle by using a simple flat zone structure instead of expensive Au—In bonding materials. The flat zone is formed through conventional processing steps on the reflection structure, eliminating the need for costly bonding materials while maintaining bonding functionality. This substitution of expensive materials with a simpler structural solution reduces both cost and production complexity.
3Illumination intensity
If a mirror system is formed on the epitaxial structure to reflect light in the required direction, then light brightness increases, but voids are formed on the epitaxial structure which affects device voltage and efficiency
Solution Approach 1:
The patent applies segmentation by dividing the reflection structure into two distinct functional zones: a curved portion that performs light reflection to increase brightness, and a flat zone that provides a void-free bonding surface. This segmentation allows each zone to fulfill its specific function without interfering with the other, thereby maintaining both light brightness and preventing void formation.
Solution Approach 2:
The patent applies local quality by giving different geometric properties to different parts of the reflection structure. The curved portion is optimized for light reflection while the flat zone is optimized for bonding. This local differentiation allows each region to have the quality needed for its specific function, resolving the contradiction between brightness enhancement and void prevention.
Data Source
AI summary
Disclosed are a light emitting diode element, a manufacturing method thereof, and a light emitting apparatus. In the light emitting diode element, a surface of a first bond layer formed on an epitaxial structure is a smooth surface without height difference. Further, a surface roughness thereof may be less than 10 nm. Therefore, when the substrate and epitaxial structure are bonded, the two bond layers are plane-to-plane bonded, and no defect such as voids occurs to ensure the bonding strength. Thereby, the bonding stability between the substrate and the epitaxial structure is ensured, and the yield of the device is improved. At the same time, there is no similar defect such as voids, which facilitates to reduce the voltage of the device and improve the photoelectric efficiency of the device.