Ruthenium Bilayer Liner and Cap for Low-Resistance BEOL Interconnects
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Solution Overview
Problem
As semiconductor circuit elements miniaturize to feature sizes below 20 nm, challenges arise in filling gaps between circuit elements and forming robust contacts, with cobalt liners and capping showing limitations beyond the 3 nm node, and ruthenium liners facing reliability issues like copper corrosion.
Innovation Solution
Implementing a ruthenium-containing bilayer as a liner and capping layer, using a bottomless ruthenium liner to prevent copper corrosion and reduce via resistance, and incorporating surfactant-assisted ruthenium processes to enhance gap fill extendibility and device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt liner and capping are used for copper gap fill, then gap fill and reliability are enhanced at 20 nm to 3 nm node, but limitations arise at 3 nm plus node and beyond
Solution Approach 1:
The patent changes the material parameter from cobalt to ruthenium for the liner and capping layer. This material substitution enables the interconnect structure to be adapted for smaller feature sizes (3 nm plus node and beyond) while maintaining reliability, thus resolving the limitation of cobalt-based systems at advanced nodes.
Solution Approach 2:
The patent employs a composite material system consisting of ruthenium liner combined with ruthenium capping layer. This composite structure provides both the gap-fill enhancement and reliability needed for advanced nodes, overcoming the single-material limitations of previous cobalt-based approaches.
2Adaptability or versatility
If ruthenium liner is used for small structures, then gap fill extendibility is improved, but copper corrosion occurs resulting in decreased device lifetimes
Solution Approach 1:
The patent introduces a ruthenium capping layer as an intermediary protective element over the copper interconnect. This capping layer acts as a barrier that prevents copper corrosion while allowing the ruthenium liner to maintain its gap-fill extendibility benefits, thus resolving the corrosion reliability issue.
Solution Approach 2:
The ruthenium capping layer is applied in advance to protect the copper interconnect from future corrosion damage. This preventive measure cushions the copper structure against environmental degradation, ensuring long-term device lifetime while preserving the gap-fill capabilities enabled by the ruthenium liner.
Data Source
AI summary
Electronic devices and methods of forming electronic devices using a ruthenium or doped ruthenium liner and cap layer are described. A liner with a ruthenium layer and a cobalt layer is formed on a barrier layer. A conductive fill forms a second conductive line in contact with the first conductive line.