Dual-Layer UBM Structure for Corrosion-Resistant Semiconductor Packages
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Solution Overview
Problem
The reliability of under bump metallurgy (UBM) structures in semiconductor packages is compromised due to corrosion, which affects the electrical connection efficiency and durability of the semiconductor package.
Innovation Solution
A semiconductor package design featuring a dual-layer UBM structure with a copper or copper alloy first layer and a nickel or nickel alloy second layer, where the second layer has a larger surface area exposed to the external environment, enhancing corrosion resistance and reliability by reducing the exposure of the copper layer to external factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer copper UBM structure is used, then electrical conductivity is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent applies composite materials by combining copper and nickel in a multi-layer UBM structure. The copper layer provides high electrical conductivity while the nickel layer provides corrosion resistance, creating a composite structure that achieves both electrical performance and environmental stability without excessive complexity
Solution Approach 2:
The UBM structure is segmented into multiple functional layers: a copper layer for electrical conductivity and a nickel layer for corrosion protection. This segmentation allows each layer to perform its specific function optimally, with the copper layer handling electrical requirements and the nickel layer handling environmental protection
2Reliability
If the copper layer is exposed to the external environment, then electrical connection efficiency is improved, but corrosion resistance deteriorates
Solution Approach 1:
The nickel layer acts as an intermediary between the copper layer and the external environment. It provides a protective barrier that prevents direct contact between corrosive external factors and the copper layer, while still allowing the copper layer to maintain its electrical connection function through the bump structure
Solution Approach 2:
The nickel layer creates an inert protective environment for the copper layer by forming a corrosion-resistant barrier. This passive protection layer shields the reactive copper from oxidation and other harmful environmental interactions, effectively creating a protected micro-environment
3Reliability
If a dual-layer UBM structure with nickel overlay is used, then corrosion resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The copper layer is formed first as a preliminary step, establishing the electrical connection foundation. Subsequently, the nickel layer is deposited over the copper layer in a planned sequence, allowing each layer to be optimized for its specific function while following a systematic manufacturing process that reduces overall complexity
Data Source
AI summary
A semiconductor package including a redistribution structure comprising a redistribution layer; a semiconductor chip electrically connected to the redistribution layer; bumps disposed on the redistribution structure; and under bump metallurgy (UBM) structures disposed between the bumps and the redistribution structure. Each of the UBM structures includes a first UBM layer including copper or a copper alloy; and a second UBM layer including nickel or nickel alloy and disposed between the redistribution structure and the first UBM layer. An area of a surface of the second UBM layer facing the first UBM layer is greater than an area of a surface of the first UBM layer facing the second UBM layer.