Copper Interconnect Barrier Surface Engineering for Enhanced Reliability
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Solution Overview
Problem
Current technologies face challenges in achieving improved electro-migration performance and interfacial adhesion for copper interconnects, particularly due to issues with copper oxide formation and contamination, which affect the adhesion between copper and dielectric layers, leading to increased resistivity and reliability concerns as metal lines narrow.
Innovation Solution
A method and system for preparing substrate surfaces by removing surface oxides and contaminants through controlled cleaning processes, followed by the selective deposition of cobalt-alloy layers using electroless deposition techniques, to enhance the metal-to-metal interface and reduce resistivity, while maintaining a controlled environment to prevent re-oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is exposed to air during processing, then copper oxide forms on the surface, but this oxide layer deteriorates adhesion between copper and dielectric layers and increases resistivity
Solution Approach 1:
The patent employs an inert atmosphere environment (nitrogen or vacuum) during the electroless deposition process to prevent copper oxidation. The substrate is transferred through a controlled environment from cleaning to deposition without exposure to air, maintaining a oxygen-free atmosphere throughout the critical processing steps.
Solution Approach 2:
The patent performs preliminary surface cleaning to remove existing copper oxide and contaminants before electroless deposition. The cleaning process includes plasma treatment and chemical cleaning steps that prepare the copper surface in advance, ensuring oxide-free conditions prior to cobalt-alloy deposition.
2Reliability
If electroless deposition is used to deposit cobalt-alloy on copper, then interfacial adhesion improves, but the process is inhibited by thin copper oxide layers on the copper surface
Solution Approach 1:
The electroless deposition process is conducted in a controlled inert atmosphere environment that prevents copper oxidation during substrate transfer and processing. This ensures the copper surface remains oxide-free, enabling successful electroless deposition of cobalt-alloy without process inhibition.
Solution Approach 2:
The patent implements preliminary copper surface cleaning through plasma treatment and chemical cleaning before electroless deposition. This preliminary action removes any oxide layers that might form, preparing the surface for successful cobalt-alloy deposition.
3Reliability
If multiple cleaning and deposition steps are implemented to prevent copper oxide, then adhesion and EM performance improve, but process complexity increases
Solution Approach 1:
The patent combines multiple cleaning and deposition steps into an integrated process sequence where substrate cleaning, drying, and electroless deposition are performed in continuous succession within a controlled environment. This merging reduces the number of separate process modules and simplifies process integration while maintaining high reliability.
Solution Approach 2:
By using a controlled inert atmosphere that prevents oxidation throughout the entire process sequence, the patent eliminates the need for separate oxidation prevention steps and intermediate storage, simplifying the overall process while maintaining electro-migration performance.
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 improves electro-migration performance and interfacial adhesion, reducing metal resistivity and enhancing the reliability of copper interconnects by ensuring clean and oxide-free surfaces for cobalt-alloy deposition, thus addressing the challenges of copper oxide formation and contamination.
Implementation Method 1
cleaning an exposed surface of an underlying metal to remove surface metal oxide
Implementation Method 2
selective deposition of cobalt-alloy layers using electroless deposition techniques
Data Source
AI summary
The embodiments fill the need to enhance electro-migration performance, provide lower metal resistivity, and improve metal-to-metal interfacial adhesion for copper interconnects by providing improved processes and systems that produce an improved metal-to-metal interface, more specifically barrier-to-copper interface. An exemplary method of preparing a substrate surface of a substrate to deposit a metallic barrier layer to line a copper interconnect structure of the substrate and to deposit a thin copper seed layer on a surface of the metallic barrier layer in an integrated system to improve electromigration performance of the copper interconnect is provided. The method includes cleaning an exposed surface of a underlying metal to remove surface metal oxide in the integrated system, wherein the underlying metal is part of a underlying interconnect electrically connected to the copper interconnect. The method also includes depositing the metallic barrier layer to line the copper interconnect structure in the integrated system, wherein after depositing the metallic barrier layer, the substrate is transferred and processed in controlled environment to prevent the formation of metallic barrier oxide. The method further includes depositing the thin copper seed layer in the integrated system, and depositing a gap-fill copper layer over the thin copper seed layer in the integrated system. An exemplary system to practice the exemplary method described above is also provided.