Copper Interconnect Protection via Alloy Diffusion
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Solution Overview
Problem
Copper metal lines in semiconductor devices are prone to degradation due to environmental exposure, leading to corrosion and oxidation, especially in upper levels of metallization where they are more susceptible during manufacturing and usage.
Innovation Solution
A protective layer comprising an alloy of copper and another metal, such as aluminum, tin, or nickel, is formed over the copper metal lines to prevent corrosion and oxidation, using techniques like annealing to create a conformal layer that covers both the top surface and sidewalls of the metal lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper metal lines are used in upper levels of metallization, then electrical performance is improved, but reliability deteriorates due to corrosion and oxidation from environmental exposure
Solution Approach 1:
A protective layer comprising aluminum, tin, nickel or their alloys is deposited over the copper metal lines to act as an intermediary barrier between the copper and the environment. This protective layer prevents direct contact between copper and corrosive environmental factors such as moisture and oxygen, thereby eliminating corrosion and oxidation issues while maintaining the electrical performance benefits of copper interconnects.
Solution Approach 2:
The invention creates a composite structure consisting of copper metal lines combined with a protective outer layer of aluminum, tin, nickel or their alloys. This composite material system combines the high electrical conductivity of copper with the environmental stability and oxidation resistance of the protective metal layer, achieving both electrical performance and reliability requirements.
2Object-affected harmful factors
If aluminum is used instead of copper in upper levels, then environmental stability is improved, but electrical performance deteriorates due to higher resistance
Solution Approach 1:
The protective layer is applied locally only to the uppermost metal lines and contact pads that are exposed to environmental factors during backend processing and usage. Lower level interconnects that are fully encapsulated can continue to use pure copper without the protective layer, optimizing the balance between electrical performance and environmental protection where needed.
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 protective layer significantly reduces the corrosion of copper metal lines to atmospheric and moisture-related degradation, improving their resistance to oxidation and maintaining electrical performance over time.
Implementation Method 1
annealing to form a protective layer comprising an alloy of the first and the second metals
Implementation Method 2
annealing to form a protective layer comprising an alloy of the first and the second metals
Implementation Method 3
depositing an alloying material layer over a top surface of the metal line
Data Source
AI summary
In one embodiment, a method of forming a semiconductor device includes forming a metal line over a substrate and depositing an alloying material layer over a top surface of the metal line. The method further includes forming a protective layer by combining the alloying material layer with the metal line.