Diffusion Barrier Structure for Copper-Tin Contact Reliability
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Solution Overview
Problem
The reliability of electrical connections in devices like FO-WLB and FO-Panel technologies is compromised due to diffusion issues between copper and tin at the contact interface, leading to voids and potential contact opens, primarily caused by a leaky diffusion barrier liner.
Innovation Solution
Implementing a diffusion barrier structure with different lateral dimensions than the redistribution layer, comprising materials like titanium-tungsten or nickel, to prevent direct contact and diffusion between copper and tin, thereby reducing void formation and enhancing connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffusion barrier liner is used between copper and tin contact surfaces, then material diffusion is initially prevented, but the liner becomes leaky during high temperature storage or operation, leading to voids and contact opens
Solution Approach 1:
The diffusion barrier structure is segmented into multiple functional layers: a lower diffusion barrier layer in direct contact with the tin pad, an upper diffusion barrier layer, and intermediate copper redistribution layers. This segmentation allows each layer to perform its specific function optimally, with the lower layer preventing tin diffusion into copper and the upper layer preventing copper diffusion into the encapsulant, thereby maintaining reliability throughout the service life.
Solution Approach 2:
The invention uses composite material structure combining different barrier materials (such as tungsten, molybdenum, or titanium nitride) with copper redistribution layers. This composite approach creates a multi-functional structure that simultaneously provides diffusion barrier properties and electrical conductivity, solving the reliability issue during high temperature operation while maintaining the intended service life.
2Reliability
If copper and tin are allowed to directly contact for electrical connection, then good electrical conductivity is achieved, but diffusion processes occur during high temperature storage leading to voids at the contact interface
Solution Approach 1:
The invention introduces diffusion barrier layers as intermediary structures between the copper redistribution layers and tin pad. These intermediate barrier layers (such as tungsten, molybdenum, or titanium nitride) prevent direct contact between copper and tin, thereby eliminating the harmful diffusion processes and void formation while still allowing electrical connection to be maintained through the barrier structure.
Solution Approach 2:
The invention extracts the harmful diffusion process by removing the direct contact interface between copper and tin. By taking out the problematic direct interaction and replacing it with controlled barrier layers, the harmful diffusion and void formation are eliminated while the essential electrical connection function is preserved through the engineered barrier structure.
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
This approach significantly reduces material diffusion, minimizing voids and delamination risks, thereby improving the long-term reliability of electrical connections by creating a more stable interface.
Implementation Method 1
a diffusion barrier structure, structured independent from the redistribution layer structure, is implemented between the Cu-RDL and the Sn-pad
Data Source
AI summary
An electrical device includes a redistribution layer structure, an inter-diffusing material contact structure and a vertical electrically conductive structure located between the redistribution layer structure and the inter-diffusing material contact structure. The vertical electrically conductive structure includes a diffusion barrier structure located adjacently to the inter-diffusing material contact structure. Further, the diffusion barrier structure and the redistribution layer structure comprise different lateral dimensions.