Solder Metallization Stack Inert Layer Corrosion
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Solution Overview
Problem
Conventional semiconductor fabrication processes face challenges in achieving high corrosion resistance and reduced stress in solder metallization stacks, particularly due to direct contact between solder metal and diffusion barrier layers, which can lead to undesired reactions and reliability issues during the die attach process.
Innovation Solution
A multi-layer diffusion barrier stack is used, where each layer serves as a barrier for the overlying layer, preventing direct contact between the solder metal and the diffusion barrier layer, and comprising a contact metal layer, diffusion barrier layer, inert layer, solder active layer, and capping layer, each with specific mechanical and chemical properties tailored to prevent metal diffusion and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thin solder layer is used to reduce stress and improve mechanical performance, then mechanical performance is improved, but the solder active layer may be fully consumed during the die attach process, leading to direct contact between liquid solder and the diffusion barrier layer
Solution Approach 1:
An inert layer is introduced between the diffusion barrier layer and the solder active layer. This inert layer acts as a mediator that prevents direct contact between the liquid solder and the diffusion barrier layer, thereby preventing undesired chemical reactions and corrosion while allowing the thin solder layer to maintain its mechanical performance benefits.
2Stress or pressure
If the solder active layer is made thin to reduce stress, then stress is reduced, but corrosion resistance deteriorates due to potential direct contact between solder metal and diffusion barrier layer
Solution Approach 1:
The inert layer serves as a protective intermediary that prevents corrosive interactions between the solder metal and the diffusion barrier layer. This allows the solder active layer to remain thin for reduced stress while the inert layer provides the necessary corrosion protection.
3Reliability
If a multi-layer diffusion barrier stack is used to prevent metal diffusion and enhance corrosion resistance, then corrosion resistance is improved, but device complexity increases
Solution Approach 1:
The diffusion barrier function is segmented into multiple specialized layers: a diffusion barrier layer for preventing metal diffusion, an inert layer for preventing corrosion, and a solder active layer for controlling solder interaction. Each layer is optimized for its specific function, achieving high reliability while maintaining manageable complexity through clear functional division.
4Ease of manufacture
If direct contact between solder metal and diffusion barrier layer is allowed, then manufacturing process is simplified, but undesired reactions occur during die attach process
Solution Approach 1:
The inert layer is positioned between the solder metal and the diffusion barrier layer to prevent undesired chemical reactions during the die attach process. This intermediary layer allows the manufacturing process to proceed without complex additional steps while eliminating the harmful chemical interactions that would occur with direct contact.
Data Source
AI summary
A semiconductor device includes a contact metal layer disposed over a semiconductor surface of a substrate, a diffusion barrier layer disposed over the contact metal layer, an inert layer disposed over the diffusion barrier layer, and a solder layer disposed over inert layer.