Cobalt Contact Metallization With RF-Controlled Reflow Gap Fill
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Solution Overview
Problem
The increasing complexity of contact openings in integrated circuit fabrication makes it challenging to fill them with metal without forming voids or seams, which can increase contact resistance and affect the reliability of the IC.
Innovation Solution
A cobalt metallization process using a co-deposition/reflow physical vapor deposition method, where RF power is used to independently control the deposition and reflow process, allowing for improved gap fill in contact openings with aspect ratios between 3 and 10 and heights greater than 60 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional metal deposition is used to fill contact openings, then the deposition process is simple, but voids or seams form in the contact openings
Solution Approach 1:
The deposition process is divided into multiple sequential steps: initial metal deposition, dielectric material deposition, and reflow processing. This segmentation allows each step to optimize for its specific function, preventing void formation while maintaining process control
Solution Approach 2:
Metal is deposited in advance to form a preliminary layer before the contact opening is fully filled. This preliminary metal layer serves as a foundation that prevents void formation during subsequent filling operations
2Reliability
If contact openings are filled with metal, then contact resistance is reduced, but voids or seams may form increasing resistance
Solution Approach 1:
The reflow process continuously processes the deposited materials at elevated temperatures to ensure complete densification and elimination of voids. This continuous thermal processing maintains uniform metal fill throughout the contact opening
Solution Approach 2:
Temperature is changed during the reflow process to optimize material flow and densification. The elevated temperature enables the dielectric material to flow and conform to the metal layer, eliminating voids while maintaining uniform fill
3Manufacturing precision
If RF power is used to independently control deposition and reflow, then process control is improved, but equipment complexity increases
Solution Approach 1:
A single RF power source is used to perform multiple functions: controlling metal deposition rate, controlling dielectric material deposition rate, and controlling reflow processing. This multi-functionality reduces the need for separate control systems while maintaining precision
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 process effectively fills contact openings, reducing the formation of voids and seams, thereby enhancing the reliability and performance of metal contacts in ICs by optimizing the deposition and reflow process.
Implementation Method 1
A cobalt metallization process using a co-deposition/reflow physical vapor deposition method
Implementation Method 2
reflowing the second metal layer using a second RF power
Data Source
AI summary
The present disclosure describes a method to a metallization process with improved gap fill properties. The method includes forming a contact opening in a dielectric layer to expose a source/drain epitaxial layer in a substrate. An aspect ratio of the contact opening is between about 3 and about 10. The method further includes forming a first metal layer in the contact opening and in contact with the source/drain epitaxial layer, forming a barrier layer on the first metal layer, forming a liner layer on the barrier layer, forming second metal layer on the liner layer to partially fill the contact opening, and forming a third metal layer on the second metal layer to fill the contact opening.