LED Bonding Layer with Diffusion Barrier and Adhesion
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Solution Overview
Problem
Light emitting diodes (LEDs) face issues such as cracking and breaking during growth substrate separation, and solder bonding materials can diffuse into the reflective or light emitting structure layers, leading to embrittlement and poor adhesiveness.
Innovation Solution
A light emitting device structure is developed with a bonding layer comprising a solder bonding layer, a diffusion barrier layer, and an adhesion layer, where the adhesion layer and diffusion barrier layer are formed using materials with a Young's Modulus of 9 GPa to 200 GPa, and the solder bonding layers are made of materials like Sn, In, Ga, Bi, and Au, to prevent cracking, breaking, and material diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a reflective layer and conductive support substrate are bonded using solder bonding materials (Au-Sn, Au-In, Pd-In, Pd-Sn), then electrical connectivity and mechanical bonding are achieved, but the solder bonding material diffuses into the light emitting structure layer causing embrittlement and poor adhesiveness
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the solder bonding material and the light emitting structure layer. This barrier layer prevents the diffusion of solder materials (Sn, In) into the semiconductor layers, thereby maintaining adhesiveness and preventing embrittlement while preserving bonding strength.
Solution Approach 2:
The bonding interface is segmented into multiple functional layers: adhesion layer, diffusion barrier layer, and solder bonding layer. This segmentation allows each layer to perform its specific function - adhesion for bonding strength, diffusion barrier for preventing material intermixing, and solder for electrical connectivity - thereby resolving the contradiction between bonding strength and adhesiveness.
2Reliability
If a diffusion barrier layer (Pt, W, Cr) is used to prevent fast diffusion of Sn or In, then material diffusion is reduced, but separation occurs due to poor adhesiveness of Sn or In
Solution Approach 1:
The bonding structure is segmented into distinct functional layers with the adhesion layer positioned between the diffusion barrier layer and the light emitting structure layer. This segmentation allows the diffusion barrier layer to focus on preventing material diffusion while the adhesion layer specializes in providing strong bonding, thereby resolving the contradiction between diffusion prevention and adhesiveness.
Solution Approach 2:
The adhesion layer serves as an intermediary that bridges the diffusion barrier layer and the light emitting structure layer. It provides strong adhesion to both interfaces while allowing the diffusion barrier layer to effectively prevent solder material diffusion, thus resolving the separation issue caused by poor adhesiveness.
3Productivity
If a buffer layer is removed through laser beam separation, then the growth substrate is successfully separated, but mechanical impact and explosive power of N2 gas cause crack or breaking in the epi-layer
Solution Approach 1:
A protective layer is formed on the light emitting structure layer before the laser separation process. This preliminary protective action shields the epi-layer from the mechanical impact and explosive force of N2 gas generated during laser beam separation, allowing successful substrate separation while preventing crack or breaking in the epi-layer.
Solution Approach 2:
The protective layer acts as a cushioning layer that absorbs and distributes the mechanical stress and explosive force generated during laser separation. This beforehand cushioning prevents direct transmission of harmful forces to the epi-layer, thereby maintaining its integrity while enabling efficient substrate separation.
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 structure effectively prevents cracking and breaking during substrate separation, and improves the embrittlement and adhesiveness of the solder bonding materials, enhancing the reliability and performance of the LED.
Implementation Method 1
the adhesion layer and diffusion barrier layer are formed using materials with a Young's Modulus of 9 GPa to 200 GPa
Implementation Method 2
a diffusion barrier layer to prevent fast diffusion of Sn or In
Implementation Method 3
an adhesion layer to improve the adhesiveness of the reflective layer and the conductive support substrate
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A light emitting device (100) is provided. The light emitting device comprises: a conductive support substrate (175); a bonding layer (170) on the conductive support substrate; a reflective layer (160) on the bonding layer; and a light emitting structure layer (135) on the reflective layer. The bonding layer comprises a solder bonding layer (173,174) on the conductive support substrate and at least one of a diffusion barrier layer (172) and an adhesion layer (171) on the solder bonding layer, the solder bonding layer, the diffusion barrier layer, and the adhesion layer being formed of a metal or an alloy of which the Young's Modulus is 9 GPa to 200 GPa.