Zinc-Copper Alloy Layer for Copper Metallization Reliability
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Solution Overview
Problem
The growth of intermetallic phases and Kirkendall voids at the interface between copper metallization and tin-containing solder in semiconductor devices leads to reliability issues, particularly at high temperatures, causing electrical failure due to separation of the metallization layer.
Innovation Solution
A zinc-copper alloy layer is galvanically deposited over the copper metallization layer to reduce the formation of intermetallic phases and voids, improving the solder joint reliability and heat dissipation during attachment to other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper metallization layer is used to provide electrical and thermal conductivity, then electrical conductivity and thermal conductivity are improved, but intermetallic phase growth and Kirkendall voids form at the interface with tin-containing solder, leading to reliability degradation
Solution Approach 1:
A zinc-containing alloy layer is introduced as an intermediary between the copper metallization layer and the tin-containing solder. This intermediate layer acts as a barrier that reduces the direct interaction between copper and tin, thereby suppressing intermetallic phase growth and Kirkendall void formation while maintaining electrical and thermal conductivity.
Solution Approach 2:
The patent employs a composite metallization structure consisting of multiple layers: a copper metallization layer for conductivity, a zinc-containing alloy layer for interface protection, and a tin-containing solder layer for bonding. This composite structure combines the advantages of each material while mitigating their individual disadvantages.
2Strength
If tin-containing solder is used for bonding due to good mechanical properties and wetting characteristics, then mechanical strength and wetting are improved, but copper-tin intermetallic phases build up at the interface, causing reliability issues
Solution Approach 1:
The zinc-containing alloy layer serves as a mediator between the tin-containing solder and the copper metallization layer. It allows the solder to maintain good mechanical strength and wetting characteristics while preventing excessive copper-tin intermetallic phase formation that would compromise electrical reliability.
3Reliability
If high temperature storage or temperature cycling is applied, then device performance is tested, but voids strongly develop at the interface of solder joints and copper metallization layer, leading to electrical failure
Solution Approach 1:
The zinc-containing alloy layer is applied beforehand to cushion against the harmful effects of high temperature and temperature cycling. It pre-establishes a protective barrier that reduces the development of Kirkendall voids during thermal stress, thereby maintaining interface integrity and preventing electrical failure.
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 zinc-copper alloy layer effectively slows the growth of intermetallic phases and voids, enhancing the reliability of semiconductor devices by improving thermal management and preventing electrical failures, especially under high-temperature conditions.
Implementation Method 1
A zinc-copper alloy layer is galvanically deposited over the copper metallization layer to reduce the formation of intermetallic phases and voids
Implementation Method 2
These voids (Krikendall voids) are formed due to different diffusion coefficients of copper and tin on the copper side of the interface
Data Source
AI summary
A method and a system for improving reliability of a semiconductor device are provided. In one embodiment, a semiconductor device is provided comprising a semiconductor chip, a metallization layer comprising a metallic material disposed over a surface of the semiconductor chip, and an alloy layer comprising the metallic material disposed over the metallization layer.