Interposer Interconnect Alloy Barrier for Reduced-Pitch Solder Joints
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Solution Overview
Problem
Current interconnects using a nickel layer barrier face challenges with limited solder amount for collapsing risk management, joint necking, and poor reliability due to ineffective resistance against intermetallic compound formation and sidewall wetting, which limits the reduction of interconnect pitch in advanced packaging.
Innovation Solution
Implementing an alloy barrier, such as an iron-based or tungsten-based binary alloy, to replace the nickel layer barrier, which reduces interconnect pitch by controlling intermetallic compound growth and sidewall wetting, ensuring improved joint yield and high-temperature solder reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel layer barrier is used in metal bumps, then the interconnect structure can be formed, but the solder amount is limited causing collapsing risk and joint necking
Solution Approach 1:
The patent changes the material parameter of the barrier layer from nickel to an alloy barrier (such as cobalt-platinum or cobalt-iridium), which fundamentally alters the intermetallic compound formation characteristics. This material substitution enables the solder joint to maintain structural integrity with reduced solder volume, directly resolving the contradiction between joint reliability and solder amount.
Solution Approach 2:
The invention employs composite alloy barriers (e.g., cobalt-platinum or cobalt-iridium combinations) instead of pure nickel. These composite materials provide superior resistance against intermetallic compound formation and sidewall wetting, allowing for reduced solder quantity while maintaining or improving joint reliability and preventing collapsing and necking issues.
2Reliability
If a nickel layer barrier is used, then the interconnect can be formed, but intermetallic compound formation and sidewall wetting occur reducing reliability
Solution Approach 1:
The patent fundamentally changes the chemical composition parameter of the barrier layer by substituting nickel with alloy barriers such as cobalt-platinum or cobalt-iridium. This material parameter change dramatically reduces the tendency to form harmful intermetallic compounds and minimizes sidewall wetting, thereby improving joint reliability without requiring increased solder amount.
Solution Approach 2:
The alloy barrier layer serves as a sacrificial protective element that prevents harmful intermetallic compound formation at the copper-solder interface. By using a thin but highly effective alloy barrier, the patent eliminates the need for thick nickel layers, reducing both material usage and the generation of harmful intermetallics, thus improving reliability.
3Productivity
If the interconnect pitch is reduced in advanced packaging, then higher density is achieved, but the nickel barrier becomes ineffective against intermetallic compound formation and sidewall wetting
Solution Approach 1:
The patent changes the material composition parameter of the barrier layer to alloy-based materials (cobalt-platinum, cobalt-iridium) which maintain effective barrier properties at smaller dimensions. This enables successful implementation of reduced interconnect pitch for higher packaging density while preserving joint reliability by preventing intermetallic compound formation and sidewall wetting even in miniaturized structures.
Solution Approach 2:
The invention applies a localized alloy barrier solution specifically at the copper-solder interface where intermetallic compound formation occurs. This targeted approach ensures that the critical barrier function is maintained at the micro-scale level of reduced-pitch interconnects, preventing reliability degradation while enabling higher packaging density through smaller pitch dimensions.
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 alloy barrier enables reduced interconnect pitch, stable microstructure, and uniform joint shape with less solder necking, providing a wider joint process window and enhanced reliability in advanced packaging.
Implementation Method 1
resistance against intermetallic compound formation
Implementation Method 2
resistance against sidewall wetting
Implementation Method 3
a metal layer (e.g., copper layer) may be formed on the UBM layer using an electrochemical deposition (ECD) system
Data Source
AI summary
An interposer module includes an interposer, a semiconductor die on the interposer, and a plurality of interconnects connecting the interposer to the semiconductor die, wherein the plurality of interconnects includes a first interconnect portion including a first alloy barrier, a second interconnect portion including a second alloy barrier, and a solder joint connecting the first interconnect portion to the second interconnect portion.