Package Bonding Structure With Fluxless IMC Interconnects
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Solution Overview
Problem
Existing package structures and fabrication methods for semiconductor devices, particularly in package on package (PoP) configurations, are inadequate in ensuring reliable bonding without the use of flux, which can lead to corrosion and short circuits due to the corrosive nature of flux residues.
Innovation Solution
A fluxless bonding method is employed using intermetallic compounds (IMCs) formed from solder and barrier layers, which react to create a stable oxide-free interface, allowing for direct contact between dies without flux, thereby preventing unwanted chemical reactions and improving bonding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flux is used in bonding, then bonding process is facilitated, but corrosion and short circuits occur due to flux residues
Solution Approach 1:
The invention extracts and eliminates flux from the bonding process entirely. By using pre-formed intermetallic compounds (IMCs) as the bonding interface, the harmful flux substance is completely removed from the system, preventing corrosion and short circuits while maintaining bonding effectiveness.
Solution Approach 2:
The invention introduces intermetallic compounds (IMCs) as an intermediary material between the first and second dies. These IMCs serve as a stable, oxide-free bonding interface that facilitates reliable bonding without requiring flux, thereby resolving the contradiction between ease of manufacture and bonding reliability.
2Reliability
If traditional bonding methods are used, then bonding can be achieved, but thermal stress increases leading to reduced bonding quality
Solution Approach 1:
The invention changes the bonding parameters by using pre-formed intermetallic compounds with controlled thickness (e.g., 1-10 micrometers) and specific material composition. This allows bonding to proceed at lower temperatures and with reduced thermal stress, improving bonding quality while maintaining reliability.
3Stability of the object's composition
If oxide layers are present on die surfaces, then natural oxidation protection occurs, but bonding reliability decreases due to unwanted chemical reactions
Solution Approach 1:
The invention converts the harmful effect of oxidation into a benefit by deliberately forming controlled intermetallic compounds through oxidation reactions. These IMCs create a stable, oxide-free bonding interface that prevents unwanted chemical reactions during bonding, thereby improving bonding reliability while maintaining surface stability.
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 method enhances bonding yield and quality by eliminating flux-related issues, reducing thermal stress, and maintaining a stable interface through the use of IMCs, which are less prone to oxidation and corrosion.
Implementation Method 1
intermetallic compounds (IMCs) formed from solder and barrier layers, which react to create a stable oxide-free interface
Implementation Method 2
maintaining a stable interface through the use of IMCs, which are less prone to oxidation and corrosion
Data Source
AI summary
A package structure is provided. The package structure includes a first interconnect structure formed over a first substrate. The package structure also includes a second interconnect structure formed below a second substrate. The package structure further includes a bonding structure between the first interconnect structure and the second interconnect structure. In addition, the bonding structure includes a first intermetallic compound (IMC) and a second intermetallic compound (IMC). The bonding structure also includes an underfill layer surrounding the bonding structure. A width of the first IMC is greater than a width of the second IMC, and the underfill layer covers a sidewall of the first IMC and a sidewall of the second IMC.