Scandium-Rare Earth Al Bonding Wire for High-Temperature Reliability
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Solution Overview
Problem
Aluminum bonding wires used in semiconductor devices experience decreased bonding reliability under high-temperature conditions due to recrystallization, leading to reduced mechanical strength and increased crystal grain size.
Innovation Solution
Incorporating 0.01 to 1% Sc and 0.01 to 0.1% of at least one or more of Y, La, Ce, and Pr into the Al bonding wire, followed by solution and thermal refining heat treatments to form a solid solution, and subsequent aging heat treatment to precipitate Al3Sc, Al3Y, Al11La3, Al11Ce3, and Al11Pr3, thereby increasing recrystallization temperature and preventing excessive recrystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Sc is added to increase wire strength, then mechanical strength is improved, but chip crack occurs during bonding
Solution Approach 1:
The patent controls the concentration parameters of alloying elements (Sc: 0.01-1%, Y/La/Ce/Pr/Nd: 0.01-0.1%) to optimize the balance between strength and bonding reliability. By precisely controlling these compositional parameters, the wire achieves sufficient mechanical strength while preventing chip crack during bonding process.
Solution Approach 2:
The patent creates a composite alloy system by combining Sc with rare earth elements (Y, La, Ce, Pr, or Nd) in specific proportions. This composite material approach allows the wire to simultaneously achieve high mechanical strength from Sc precipitation and bonding reliability through rare earth element reinforcement, resolving the contradiction between strength and bonding performance.
2Strength
If aging heat treatment is performed to precipitate Al3Sc and increase strength, then mechanical strength is improved, but recrystallization occurs at high temperature reducing strength
Solution Approach 1:
The rare earth elements (Y, La, Ce, Pr, or Nd) act as intermediary substances that modify the recrystallization behavior of the Al-Sc system. These intermediaries raise the recrystallization temperature and suppress grain growth during high-temperature service, thereby maintaining the strength gained from Al3Sc precipitation while improving thermal stability.
Solution Approach 2:
The patent changes the thermal parameters by introducing rare earth elements that fundamentally alter the recrystallization temperature and kinetics of the alloy. This parameter change enables the wire to maintain its strengthened state at high temperatures where conventional Al-Sc alloys would recrystallize and lose strength.
3Reliability
If high purity Al is used, then electrical conductivity is improved, but wire softens at high temperature
Solution Approach 1:
The patent creates a composite alloy structure by adding small amounts of Sc and rare earth elements to high purity Al. This composite approach maintains the excellent electrical conductivity of pure aluminum while introducing precipitation hardening mechanisms that provide high-temperature strength, thus resolving the contradiction between conductivity and thermal strength.
Solution Approach 2:
The patent makes controlled changes to the compositional parameters by introducing trace amounts of alloying elements (Sc: 0.01-1%, rare earth: 0.01-0.1%) that dramatically improve high-temperature strength through precipitation hardening, while minimizing the impact on electrical conductivity to maintain the advantages of aluminum bonding wire.
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 maintains mechanical strength and ensures sufficient bonding reliability under high-temperature conditions by suppressing recrystallization, as evidenced by maintained bond shear force and reduced chip cracks.
Implementation Method 1
When an alloy of containing scandium (Sc) is used and Sc is precipitated as Al3Sc the strength of the Al bonding wire can be increased
Implementation Method 2
when the semiconductor device is continuously used under a high temperature environment, recrystallization of the Al bonding wire further proceeds, and the strength of the wire is decreased
Implementation Method 3
the Al bonding wire containing 0.01 to 1% of Sc further contains 0.01 to 0.1% in total of at least one or more of yttrium, lanthanum, cerium, praseodymium and neodymium
Implementation Method 4
Al3Y, Al11La3, Al11Ce3, and Al11Pr3 precipitates are formed
Data Source
AI summary
There is provided an Al bonding wire which can achieve a sufficient bonding reliability of bonded parts of the bonding wire under a high temperature state where a semiconductor device using the Al bonding wire is operated. The Al bonding wire contains 0.01 to 1% of Sc, and further contains 0.01 to 0.1% in total of at least one or more of Y, La, Ce, Pr and Nd. With regard to the Al bonding wire, a recrystallization temperature thereof is increased, so that the proceeding of recrystallization of the bonding wire can be suppressed, and strength of the wire can be prevented from being decreased even when the semiconductor device is continuously used under a high temperature environment. Accordingly, the Al bonding wire can sufficiently secure the reliability of the bonded parts after a high-temperature long-term hysteresis.