Semiconductor Element Bonding Layer Thermal Conductivity
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Solution Overview
Problem
Light-emitting diode (LED) elements face reduced light extraction efficiency and poor heat dissipation due to the absorption of light in growth substrates and low thermal conductivity, respectively, which are exacerbated by the use of eutectic bonding with AuSn, resulting in a sandwich structure with low thermal conductivity adjacent to the semiconductor layer.
Innovation Solution
A method involving a supporting substrate with high thermal conductivity, where a first bonding layer with 21 wt% Sn content and a second bonding layer with a Ni eutectic underlayer and Au surface layer are used to form a eutectic crystal, ensuring a high Au concentration layer is adjacent to the semiconductor layer, enhancing thermal conductivity and heat dissipation through heating pressure-bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eutectic bonding with AuSn is used to bond the semiconductor layer to the supporting substrate, then bonding reliability is improved, but thermal conductivity in the bonding portion deteriorates due to the formation of an Au-rich layer with low thermal conductivity adjacent to the semiconductor layer
Solution Approach 1:
The patent applies local quality by creating a specific compositional gradient within the bonding layer. The bonding layer has higher Au concentration adjacent to the semiconductor layer and higher Sn concentration toward the supporting substrate, forming a non-uniform local composition that optimizes both bonding reliability and thermal conductivity at different locations within the bonding interface
Solution Approach 2:
The patent changes the concentration parameters of Au and Sn within the bonding layer. By controlling the Au concentration to be 5-50 wt% and Sn concentration to be 50-95 wt%, with the Au concentration decreasing and Sn concentration increasing from the semiconductor layer side toward the supporting substrate, the patent achieves optimal thermal conductivity and bonding properties through parameter optimization
2Strength
If a eutectic crystal is formed with equal proportions of Au and Sn, then bonding strength is improved, but thermal conductivity deteriorates because Sn has lower thermal conductivity than Au
Solution Approach 1:
The patent applies local quality by creating a specific compositional gradient within the bonding layer. The bonding layer has higher Au concentration adjacent to the semiconductor layer and higher Sn concentration toward the supporting substrate, forming a non-uniform local composition that optimizes both bonding reliability and thermal conductivity at different locations within the bonding interface
Solution Approach 2:
The patent changes the concentration parameters of Au and Sn within the bonding layer. By controlling the Au concentration to be 5-50 wt% and Sn concentration to be 50-95 wt%, with the Au concentration decreasing and Sn concentration increasing from the semiconductor layer side toward the supporting substrate, the patent achieves optimal thermal conductivity and bonding properties through parameter optimization
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 approach improves heat dissipation efficiency and reliability of the semiconductor element by creating a high thermal conductivity layer adjacent to the semiconductor layer, effectively addressing the limitations of eutectic bonding in LED manufacturing.
Implementation Method 1
a eutectic crystal such as AuSn is used to bond the semiconductor layer to a supporting substrate with thermal conductivity. This bonding is referred to as 'eutectic bonding' in this specification. In eutectic bonding, the eutectic crystal material is melted or softened at a high temperature at or above the melting point of the AuSn used in bonding
Implementation Method 2
Sn has a low(er) thermal conductivity (64 W/m·K) compared with that of Au (295 W/m·K), and so the layer adjacent to the semiconductor layer has low thermal conductivity. As a result, dispersion of heat from the semiconductor layer is impeded
Data Source
Figure 1
Figure 2A~3
Figure 4A~4B
AI summary
A method of manufacturing a semiconductor element includes forming a first bonding layer (13) containing a metal, which forms a eutectic crystal with Au, on a first substrate (11) to provide a first laminated body. The method also includes forming an element structure layer having a semiconductor layer (23) on a second substrate (21). The method also includes forming a second bonding layer (25) on the element structure layer (23) to provide a second laminated body. The second bonding layer (25) has a metal underlayer (25A) containing a metal, which forms a eutectic crystal with Au. The second bonding layer also has a surface layer (25B) that contains Au. The method also includes performing heating pressure-bonding on the first and second laminated bodies with the first and second bonding layers facing each other. The heating temperature of the second substrate (21) in the heating pressure-bonding is higher than the heating temperature of the first substrate (11).