Zinc-Modified Copper Pillar Corrosion Resistance
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Solution Overview
Problem
The existing methods for fabricating semiconductor devices with copper pillars over vias face challenges in ensuring reliable electrical contact and corrosion resistance, particularly at the interface between the copper pillars and the titanium tungsten (TiW) layer, which can lead to reduced reliability and increased risk of electromigration.
Innovation Solution
The method involves forming a copper pillar with a bottom portion that includes interdiffused zinc, which forms brass, providing enhanced corrosion resistance and improving electromigration reliability, or using a sacrificial zinc layer to prevent corrosion of the copper pillar, while extending the perimeter of the TiW and copper pillar to ensure full surface contact with the vias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a copper pillar is formed directly over a TiW via, then the fabrication process is simple, but corrosion resistance and electromigration reliability are reduced
Solution Approach 1:
The copper pillar structure is segmented into multiple functional zones: a pure copper upper portion for electrical connection and a zinc-containing lower portion for corrosion protection. This segmentation allows each zone to perform its specific function optimally while maintaining overall structural integrity
Solution Approach 2:
The copper pillar incorporates a composite structure with different material compositions at different heights. The upper portion is pure copper for conductivity, while the lower portion contains zinc (5-30 atomic percent) to form a protective interface layer with TiW, creating a composite material system that combines electrical performance with corrosion resistance
2Reliability
If the TiW and copper pillar perimeter is extended beyond the via, then full surface contact is ensured, but the device complexity increases
Solution Approach 1:
The TiW layer and copper pillar are designed with an extended perimeter that protrudes beyond the via opening before final polishing. This preliminary extension ensures complete via coverage and full surface contact is achieved automatically during the planarization process, eliminating the need for additional alignment steps
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 approach enhances the electrical reliability of the packaged semiconductor device by ensuring complete surface contact and reducing corrosion, thereby improving the device's performance and longevity.
Implementation Method 1
the bottom portion includes an interdiffused zinc, which forms brass
Implementation Method 2
using a sacrificial zinc layer to prevent corrosion of the copper pillar
Data Source
AI summary
A device includes a semiconductor die including a via, a layer of titanium tungsten (TiW) in contact with the via, and a copper pillar including a top portion and a bottom portion. The bottom portion is in contact with the layer of TiW. The copper pillar includes interdiffused zinc within the bottom portion.