Semiconductor Light Emitting Device Electrode Structure
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in achieving optimal soldering strength and reliability due to issues with thermal expansion and material compatibility, leading to cracks and fractures during bonding processes.
Innovation Solution
The implementation of a semiconductor light emitting device structure with a lower electrode layer having a specific thermal expansion coefficient for crack prevention and an upper electrode layer with a higher thermal expansion coefficient to prevent fracture, along with an electrical connecting part for stable electrical connections, and the use of Sn-based soldering layers with an Au anti-oxidation layer to enhance bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal reflective film structure with high reflectance is used, then light reflection efficiency is improved, but soldering strength and reliability deteriorate due to thermal expansion mismatch
Solution Approach 1:
The electrode structure is divided into multiple functional layers: a lower electrode layer (e.g., Ni or W) for mechanical support and thermal expansion matching, an intermediate reflective layer (e.g., Ag or Al) for light reflection, and an upper bonding layer (e.g., Au) for soldering. This segmentation allows each layer to optimize its specific function without compromising overall reliability.
Solution Approach 2:
The patent employs composite electrode structures combining multiple materials with different properties. The lower electrode layer uses materials with thermal expansion coefficients matching the semiconductor substrate, while the reflective layer provides optical performance, and the upper layer ensures bonding strength. This composite approach resolves the contradiction between light reflection efficiency and soldering reliability.
2Reliability
If the thermal expansion coefficient of the electrode layer is increased to match substrate expansion, then cracking during bonding is reduced, but fracture resistance deteriorates
Solution Approach 1:
The electrode is segmented into a lower layer with thermal expansion coefficient matching the substrate (for crack prevention) and an upper layer with higher strength properties (for fracture resistance). This segmentation allows each layer to address specific mechanical challenges without compromising overall structural integrity.
Solution Approach 2:
Different regions of the electrode structure have different material properties optimized for their specific functions. The lower electrode layer has mechanical properties matched to the substrate for stress distribution, while the upper bonding layer has enhanced strength properties for fracture resistance and soldering reliability.
3Loss of energy
If a non-conductive reflective film is used instead of metal, then light absorption by metal is reduced, but current spreading capability deteriorates
Solution Approach 1:
The electrode structure is segmented to separate the light reflection function from the current spreading function. The reflective layer (conductive or non-conductive) handles light reflection, while the lower electrode layer and bonding pads provide current spreading pathways. This functional segmentation resolves the contradiction between reducing light absorption and maintaining current spreading capability.
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 configuration improves the bonding strength and reliability of semiconductor light emitting devices by reducing thermal expansion-related issues and ensuring stable electrical connections, while also optimizing the soldering process for better performance and yield.
Implementation Method 1
a lower electrode layer having a first thermal expansion coefficient for preventing cracks in the semiconductor light emitting device during bonding
Implementation Method 2
an upper electrode layer having a second thermal expansion coefficient larger than the first thermal expansion coefficient for preventing fracture of the lower electrode layer
Implementation Method 3
the use of Sn-based soldering layers with an Au anti-oxidation layer to enhance bonding strength
Implementation Method 4
Au anti-oxidation layer
Data Source
AI summary
Disclosed is a semiconductor light emitting device, including: a plurality of semiconductor layers; a non-conductive reflective film coupled to the plurality of the semiconductor layers; and one or more electrodes formed on the non-conductive reflective film and electrically connected to the plurality of semiconductor layers, in which the one or more electrodes respectively include a lower electrode layer for reflecting light generated in the active layer and then passed the non-conductive reflective film, and an upper electrode layer arranged on the lower electrode layer for preventing a foreign material from penetrating into the lower electrode layer.