Cu Bonding Wire with Pt and Dopants for High IMC Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The low formation rate of Cu—Al intermetallic compounds (IMC) in the bonding interface between Cu bonding wires and Al alloy electrodes in small-ball bonding leads to performance degradation, including non-stick failure, ball separation, and reduced long-term reliability of ball bonds, especially in high-temperature environments.
Innovation Solution
Incorporating 0.1 mass % to 1.3 mass % of Pt and at least one dopant from the first dopant group, consisting of In, Ga, and Ge, into the Cu bonding wire to enhance the formation rate of Cu—Al IMC, while maintaining appropriate ball hardness to prevent Al splashing and Si chip damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bare Cu wires are used for small-ball bonding, then cost is reduced and manufacturing simplicity is improved, but the formation rate of Cu-Al IMC is low leading to poor bonding reliability
Solution Approach 1:
The patent uses composite material structure by combining Cu core with Pt coating layer, where the Pt layer (0.01-1 mass%) acts as a protective and reactive interface that promotes Cu-Al IMC formation, while the Cu core provides electrical conductivity and cost benefits. This composite structure resolves the contradiction by adding a thin functional layer that enables reliable bonding without completely abandoning the simplicity of bare Cu wires.
Solution Approach 2:
The patent changes the chemical composition parameters of the bonding wire by controlling Pt content (0.01-1 mass%) and adding specific dopants (In: 0.003-0.03 mass%, Ga: 0.003-0.03 mass%, or Ge: 0.003-0.03 mass%) to optimize the formation rate of Cu-Al IMC. This parameter optimization allows the wire to achieve reliable bonding performance while maintaining manufacturing feasibility.
2Reliability
If Pt is added to Cu bonding wire to improve IMC formation rate, then bonding reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent optimizes Pt content within a specific range (0.01-1 mass%) to achieve the minimum effective concentration for improving IMC formation rate. By controlling the Pt concentration parameter and combining it with small amounts of dopants (In/Ga/Ge), the patent achieves reliable bonding without excessive Pt addition, thus limiting the increase in manufacturing complexity and cost.
Solution Approach 2:
The patent creates a multi-component composite wire structure (Cu-Pt-In/Ga/Ge) where each element serves a specific function. The Pt provides IMC formation promotion, while the dopants (In, Ga, or Ge) further enhance the reaction characteristics. This composite approach achieves reliable bonding with a controlled, manageable structure rather than simple Pt addition.
3Object-affected harmful factors
If ball hardness is increased to prevent Al splashing, then protection of Si chip is improved, but the formation rate of Cu-Al IMC may be affected
Solution Approach 1:
The patent changes the chemical composition parameters (adding Pt and dopants In/Ga/Ge) to modify the ball's mechanical and chemical properties simultaneously. This composition optimization achieves appropriate ball hardness to prevent Al splashing while maintaining or enhancing the Cu-Al IMC formation rate, resolving the contradiction between mechanical protection and chemical reactivity.
Solution Approach 2:
The composite Cu-Pt-In/Ga/Ge structure provides synergistic effects where Pt and dopants enhance both the mechanical strength (ball hardness) and chemical reactivity (IMC formation rate). The composite material achieves dual functionality: preventing Al splashing through increased hardness while promoting reliable bonding through enhanced intermetallic compound formation.
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 bonding wire achieves an improved formation rate of Cu—Al IMC to 80% or above, ensuring enhanced bonding strength and reliability, with no Al splashing or Si chip damage, and refined crystal structure for improved hardness and grain refinement effects.
Implementation Method 1
the formation rate of Cu—Al IMC formed in a bonding interface between a Cu bonding wire and Al alloy electrode
Implementation Method 2
Cu—Al intermetallic compound (Cu—Al IMC) formed in a bonding interface
Implementation Method 3
heat-melting a wire tip by arc heat input, forming a ball (FAB: Free Air Ball) by surface tension
Implementation Method 4
forming a ball (FAB: Free Air Ball) by surface tension
Implementation Method 5
a thermosonic bonding process is used commonly
Implementation Method 6
pressure-bonding the ball portion (hereinafter referred to as ball bonding) to an electrode
Implementation Method 7
refined crystal structure for improved hardness and grain refinement effects
Data Source
AI summary
The present invention provides a bonding wire for a semiconductor device suitable for cutting-edge high-density LSIs and on-vehicle LSIs by improving the formation rate of Cu—Al IMC in ball bonds. A bonding wire for a semiconductor device contains Pt of 0.1 mass % to 1.3 mass %, at least one dopant selected from a first dopant group consisting of In, Ga, and Ge, for a total of 0.05 mass % to 1.25 mass %, and a balance being made up of Cu and incidental impurities.