Cu Alloy Bonding Layer for Semiconductor Thermal Reliability
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Solution Overview
Problem
Existing semiconductor devices face reliability issues in high temperature environments due to the limitations of traditional solder materials like Pb—Sn, Sn—Ag, and Sn—Ag—Cu, which have low melting points and inadequate long-term bonding reliability.
Innovation Solution
A semiconductor device with a bonding layer composed of a Cu-based alloy and a first metal (such as Sn, Zn, or In) is used, where the alloy's melting point is higher than the first metal's, allowing for robust bonding at lower temperatures and incorporating fillet portions for stress relief and crack repair, enhancing thermal conductivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional solder materials (Pb-Sn, Sn-Ag, Sn-Ag-Cu) are used for bonding semiconductor elements, then the bonding process is simple and well-established, but the long-term reliability in high temperature environments deteriorates due to low melting points
Solution Approach 1:
The patent changes the material parameters by transitioning from traditional low-melting-point solders to Cu-based alloys with higher melting points. Specifically, it uses Cu-Sn, Cu-Zn, or Cu-In alloys where the melting point is elevated while maintaining bonding capability, directly resolving the contradiction between reliability and temperature resistance
Solution Approach 2:
The patent employs composite material strategies by creating eutectic alloys with specific compositions (e.g., Cu-5wt%Sn, Cu-10wt%Sn) that combine the advantages of high melting point with good bonding properties. The bonding layer is formed as a composite structure involving Cu intermetallic compounds that provide both thermal stability and mechanical bonding
2Adaptability or versatility
If Pb-free solder materials (Sn-Ag, Sn-Ag-Cu) are adopted, then environmental compliance is improved, but the bonding reliability in high temperature environments deteriorates
Solution Approach 1:
The patent changes the compositional parameters by adopting Cu-based alloys instead of Sn-based Pb-free solders. This parameter change achieves both environmental compliance (Pb-free) and improved high-temperature reliability through the higher melting point and superior thermal stability of Cu-based materials
Solution Approach 2:
The patent applies local quality by optimizing the specific composition of Cu-based alloys for different application requirements. For example, Cu-5wt%Sn provides eutectic bonding at 227°C with high reliability, while Cu-10wt%Sn offers even higher melting point for extreme temperature applications, allowing tailored solutions for different environmental compliance and reliability needs
3Temperature
If higher melting point bonding materials are used, then thermal stability is improved, but the bonding temperature requirement increases
Solution Approach 1:
The patent changes the material parameters by selecting Cu-based alloys with eutectic compositions that have specific melting points (227°C for Cu-5wt%Sn, 900°C for Cu-10wt%Sn). These parameter changes provide thermal stability while keeping bonding temperatures manageable through eutectic reactions that occur at lower temperatures than the melting points of pure components
Solution Approach 2:
The patent utilizes phase transitions, specifically eutectic melting and solidification, to achieve bonding. The eutectic reaction allows the alloy to melt and bond at a temperature lower than the melting points of the individual components, providing thermal stability in the bonded state while maintaining ease of manufacture through controlled phase transition during the bonding process
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 solution provides improved long-term reliability and heat dissipation in high temperature environments by forming a strong, uniform bonding layer with a higher melting point, reducing thermal resistance and preventing defects like cracks through effective stress management and repair mechanisms.
Implementation Method 1
enhancing thermal conductivity and reliability
Implementation Method 2
incorporating fillet portions for stress relief and crack repair
Data Source
AI summary
According to one embodiment, a semiconductor device includes a semiconductor element, an interconnection layer, and a bonding layer. The interconnection layer includes Cu. The bonding layer includes a first alloy that is an alloy of Cu and a first metal other than Cu between the semiconductor element and the interconnection layer. A melting point of the first alloy is higher than a melting point of the first metal.