Ruthenium Interconnect Structure With Selective Barrier Deposition
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Solution Overview
Problem
As semiconductor devices continue to scale to smaller sub-micron sizes, reducing contact resistance while maintaining desired contact reliability becomes an increasing challenge in interconnect structures.
Innovation Solution
The formation of interconnect structures involves the use of conductive features with direct metal-to-metal contact, where conductive features are formed without a barrier layer between the conductive material and dielectric layer, and the use of a blocking layer to prevent metal diffusion, along with a selective deposition of a barrier layer on dielectric surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier layer is inserted between conductive material and dielectric layer, then metal diffusion is prevented, but contact resistance increases
Solution Approach 1:
The patent removes the barrier layer from the contact structure, extracting the harmful element that increased contact resistance. By eliminating the barrier layer entirely and relying on the blocking layer to prevent metal diffusion, the conductive material achieves direct contact with the dielectric layer, thereby reducing contact resistance while maintaining diffusion prevention through the selective blocking layer deposition.
Solution Approach 2:
The patent applies local quality by selectively depositing the blocking layer only on specific dielectric surfaces where metal diffusion needs to be prevented, rather than using a universal barrier layer throughout the contact structure. This selective localization allows direct metal-to-dielectric contact in critical areas while providing diffusion protection only where necessary.
2Object-affected harmful factors
If direct metal-to-metal contact is implemented, then contact resistance is reduced, but metal diffusion control becomes more challenging
Solution Approach 1:
The patent introduces a blocking layer as an intermediary element that selectively prevents metal diffusion at the dielectric interface without interfering with the direct metal-to-metal contact between conductive layers. This mediator allows the conductive materials to maintain direct contact for low resistance while the blocking layer stands between the metal and dielectric to prevent unwanted diffusion.
Solution Approach 2:
The blocking layer is selectively deposited only on specific dielectric surfaces rather than forming a complete barrier around the conductive material. This localized application provides diffusion protection precisely where metal diffusion to the dielectric is problematic, while leaving other interfaces open for direct metal contact to maintain low resistance.
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
This approach reduces contact resistance and enhances contact reliability by ensuring direct metal contact and preventing metal diffusion, thereby improving the performance of semiconductor devices.
Implementation Method 1
a blocking layer to prevent metal diffusion
Implementation Method 2
conductive features with direct metal-to-metal contact
Data Source
AI summary
A method for forming an interconnect structure including forming a plurality of ruthenium-based contact vias in a first interlayer dielectric, forming a second interlayer dielectric over the first interlayer dielectric, forming a first dielectric layer over the second interlayer dielectric, etching a first opening and a second opening through the first dielectric layer to expose at least one ruthenium-based contact via and a plurality of ruthenium-based contact vias, respectively, selectively depositing a tantalum nitride barrier layer on sidewalls of the first and second openings, excluding exposed surfaces of the ruthenium-based contact vias, depositing a ruthenium-based liner layer in the first and second openings, the ruthenium-based liner layer having a bottom portion thicker than a sidewall portion, filling the first and second openings with copper to form first and second conductive features, respectively, in direct contact with the ruthenium-based contact vias, selectively depositing a ruthenium-based cap layer over the first and second conductive features, the ruthenium-based cap layer forming a protrusion, and forming a second dielectric layer over the first dielectric layer, the second dielectric layer containing a third conductive feature comprising copper in direct contact with the ruthenium-based cap layer.