Composite Pad Structure with Barrier Layer for Flip Chip Reliability
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Solution Overview
Problem
In flip chip package technology, gold bumps easily diffuse into aluminum metal layers under high temperature and pressure, forming intermetallic compounds and causing defects like slits, which deteriorate adhesion and electrical connections, affecting the reliability and lifetime of semiconductor devices.
Innovation Solution
A semiconductor structure with a composite pad structure that includes a barrier layer, preventing material diffusion between the bump and the pad, comprising a substrate, insulating layer, composite pad structure with a first and second conductive layer, and a passivation layer, where the barrier layer is formed using materials like titanium/titanium nitride to prevent intermetallic compound formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold bumps are electrically connected to aluminum bonding pads via an aluminum metal layer, then electrical connection is established, but gold diffuses into the aluminum layer under high temperature and pressure forming intermetallic compounds that create slits and deteriorate adhesion
Solution Approach 1:
A barrier layer is introduced as an intermediary between the aluminum conductive layer and the gold bump. This barrier layer prevents direct contact between aluminum and gold, thereby blocking the diffusion path that leads to intermetallic compound formation. The barrier layer acts as a mediator that maintains electrical connection while preventing the harmful chemical reaction between aluminum and gold under high temperature and pressure conditions.
Solution Approach 2:
The pad structure is transformed from a single-material aluminum layer to a multi-layer composite structure consisting of an aluminum conductive layer, a barrier layer, and potentially other layers. This composite structure combines the electrical conductivity of aluminum with the diffusion-blocking properties of the barrier layer, achieving both electrical connection and prevention of intermetallic compound formation.
2Reliability
If a barrier layer is inserted between the bump and the composite pad structure, then material diffusion is prevented and intermetallic compound formation is avoided, but the structure becomes more complex
Solution Approach 1:
The pad structure is segmented into multiple functional layers: a first conductive layer for electrical connection, a barrier layer for diffusion prevention, and a second conductive layer for additional electrical connection. This segmentation allows each layer to perform its specific function independently, achieving reliable adhesion and preventing intermetallic compound formation while maintaining a systematic and organized 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 solution establishes a strong adhesion and good electrical connection between the composite pad structure and the bump, enhancing the reliability and lifetime of semiconductor devices by preventing material diffusion and intermetallic compound formation.
Implementation Method 1
a barrier layer, and a second conductive layer that are disposed sequentially... the barrier layer is formed using materials like titanium/titanium nitride to prevent intermetallic compound formation
Data Source
AI summary
A semiconductor structure including a substrate, an insulating layer, a composite pad structure, a passivation layer, and a bump is provided. A circuit structure is disposed on the substrate. The insulating layer covers the substrate and has a first opening exposing the circuit structure. The composite pad structure includes a first conductive layer, a barrier layer, and a second conductive layer which are sequentially disposed. The composite pad structure is disposed on the insulating layer and fills the first opening to electrically connect to the circuit structure. The passivation layer covers the composite pad structure and has a second opening exposing the composite pad structure. The bump fills the second opening and electrically connects to the composite pad structure.