Light-Emitting Device Reflective Structure Metal Mesa
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Solution Overview
Problem
AuSn alloy used in optoelectronic device packaging exhibits low melting point and good ductility, leading to volcano defects during laser dicing, which compromises the reliability of the device's mounting on a package board due to the high operating temperatures involved.
Innovation Solution
A manufacturing method for a light-emitting device that includes forming semiconductor mesas, bonding a substrate, creating a reflective structure, applying a metal layer with a low melting point (such as AuSn) on the reflective structure, and patterning it to form metal mesas, which helps in avoiding volcano defects by maintaining structural integrity during laser dicing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AuSn alloy is applied for soldering in optoelectronic device package due to its low melting point and good ductility, then the device can be bonded reliably, but volcano defects form during laser dicing due to the high laser operating temperature exceeding the alloy's melting point
Solution Approach 1:
The patent divides the metal structure into two distinct parts: a reflective structure layer (first metal layer) and a metal mesa (second metal layer). The reflective structure layer serves as a heat barrier during laser dicing, while the metal mesa maintains bonding functionality. This segmentation allows the device to benefit from both low melting point bonding and resistance to laser-induced volcano defects.
Solution Approach 2:
The reflective structure layer acts as an intermediary between the laser beam and the AuSn alloy during dicing. It absorbs and reflects the laser energy, preventing direct heating of the AuSn alloy that would cause volcano defects. This intermediary layer enables the use of AuSn alloy for reliable bonding without suffering from its low melting point during high-temperature laser processing.
2Reliability
If a metal layer with low melting point is used to maintain ductility for bonding, then good bonding reliability is achieved, but the metal layer cannot withstand high-temperature laser dicing processes
Solution Approach 1:
The metal structure is segmented into a reflective structure layer and a metal mesa. The reflective structure layer is designed to withstand high laser temperatures by absorbing and reflecting laser energy, while the metal mesa maintains the low melting point characteristics needed for reliable bonding. This segmentation resolves the contradiction between temperature resistance and bonding reliability.
Solution Approach 2:
Different regions of the metal structure are assigned different properties: the reflective structure layer has high temperature resistance and laser reflectivity, while the metal mesa has low melting point and high ductility. This local differentiation of material properties allows the device to simultaneously achieve temperature resistance during dicing and bonding reliability.
3Manufacturing precision
If the entire metal layer is patterned to form metal mesas, then precise alignment with light-emitting mesas is achieved, but the structural integrity during laser dicing is compromised due to complete exposure of the low melting point material
Solution Approach 1:
The metal structure is segmented into a continuous reflective structure layer and discrete metal mesas. The reflective structure layer remains continuous and intact, providing structural integrity and heat barrier functionality during laser dicing. The metal mesas are selectively formed only where needed for electrical connections, maintaining precise alignment with light-emitting mesas while minimizing exposure of low melting point material.
Solution Approach 2:
The reflective structure layer is formed first as a continuous barrier before the metal mesas are patterned. This preliminary action ensures that the heat barrier is already in place to protect against laser-induced volcano defects, while subsequent patterning of metal mesas achieves precise alignment without compromising the underlying protective layer.
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 method effectively prevents volcano defects and ensures reliable mounting of light-emitting devices on package boards by utilizing a metal layer with a low melting point that maintains structural integrity during high-temperature laser dicing processes.
Implementation Method 1
forming a reflective structure on the first substrate
Data Source
AI summary
A manufacturing method of a light-emitting device is disclosed. The method provides for patterning a semiconductor stack on a first substrate in order to form multiple light-emitting mesas. A second substrate is then bonded to the multiple light-emitting mesas and a reflective structure is formed on the first substrate. A metal layer is then applied on the reflective structure and the metal layer is patterned to form multiple metal mesas corresponding to the multiple light-emitting mesas, with a portion of the reflective structure being exposed.