Copper Surface Engineering for Selective Cobalt-Alloy Deposition
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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 cobalt-alloy capping layers, leading to increased resistivity and reliability concerns as metal lines narrow.
Innovation Solution
A method and system for preparing a substrate surface to selectively deposit a cobalt-alloy material on copper interconnects, involving the removal of contaminants and metal oxides in a reducing environment, followed by electroless deposition of a thin cobalt-alloy layer to enhance adhesion and reduce electro-migration, using an integrated system with controlled ambient processing to prevent copper oxide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is exposed to air during processing, then copper oxide forms on the surface, but adhesion between copper and cobalt-alloy deteriorates
Solution Approach 1:
The patent employs an inert atmosphere environment (nitrogen or vacuum) throughout the processing sequence to prevent copper oxidation. The copper surface is prepared, coated with cobalt-alloy, and processed entirely within the inert atmosphere chamber, eliminating exposure to oxygen that would cause harmful oxide formation and adhesion deterioration.
Solution Approach 2:
The patent performs preliminary surface preparation of copper (cleaning and activation) before cobalt-alloy deposition within the inert atmosphere. This preliminary action ensures the copper surface is in optimal condition for adhesion before the protective cobalt-alloy layer is applied, preventing oxide formation that would compromise the interface.
2Reliability
If conventional multi-step cleaning processes are used to remove contaminants, then surface cleanliness improves, but processing time and complexity increase
Solution Approach 1:
The patent combines multiple cleaning and preparation steps into a single integrated process sequence performed within the inert atmosphere chamber. Surface cleaning, activation, and cobalt-alloy deposition are merged into one continuous operation, eliminating the need for separate processing steps and reducing overall processing time while maintaining surface cleanliness.
Solution Approach 2:
The inert atmosphere chamber serves multiple functions: it prevents oxidation, provides a controlled environment for cleaning, enables surface activation, and facilitates cobalt-alloy deposition. This multi-functional approach consolidates what would otherwise require multiple separate equipment and process steps.
3Productivity
If thin copper interconnects are used to increase integration density, then device capacity improves, but electro-migration resistance deteriorates
Solution Approach 1:
The patent creates a composite metal interface structure by depositing cobalt-alloy on copper. This composite structure combines the high conductivity of thin copper interconnects with the electro-migration resistance of cobalt-alloy, allowing thin lines for high integration density while the cobalt-alloy layer protects against electro-migration failures.
Solution Approach 2:
The cobalt-alloy layer acts as an intermediary between the copper interconnect and the surrounding environment. It mediates the electro-migration stress by providing a protective barrier that prevents copper atom migration while allowing the thin copper structure to maintain its electrical function and support high integration density.
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 solution improves electro-migration performance and interfacial adhesion, reducing metal resistivity and enhancing the reliability of copper interconnects by ensuring good adhesion between copper and cobalt-alloy layers, thus addressing the challenges posed by narrowing metal lines and contamination.
Implementation Method 1
removal of contaminants and metal oxides from the substrate surface in the integrated system in a reducing environment
Implementation Method 2
selectively depositing the thin layer of cobalt-alloy material on the copper surface of the copper interconnect in the integrated system
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 copper-to-cobalt-alloy interface. An exemplary method of preparing a substrate surface of a substrate to selectively deposit a thin layer of a cobalt-alloy material on a copper surface of a copper interconnect of the substrate in an integrated system to improve electromigration performance of the copper interconnect is provided. The method includes removing contaminants and metal oxides from the substrate surface in the integrated system, and reconditioning the substrate surface using a reducing environment after removing contaminants and metal oxides in the integrated system. The method also includes selectively depositing the thin layer of cobalt-alloy material on the copper surface of the copper interconnect in the integrated system after reconditioning the substrate surface. An exemplary system to practice the exemplary method described above is also provided.