Cobalt Interconnect Oxidation Removal for Low Resistance
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Solution Overview
Problem
As technology nodes continue to shrink beyond 7 nanometers, cobalt contacts in semiconductor devices are prone to oxidation, leading to increased contact resistance, which is a challenge in forming efficient middle-of-line (MOL) interconnects.
Innovation Solution
The method involves forming cobalt interconnect structures with an increased contact area by removing cobalt oxidation layers and using a process that includes forming a contact with a cobalt core and a liner layer, followed by etching to create openings around the cobalt core, and depositing a metal liner and conductive metal to reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt contacts are used in semiconductor devices, then conductivity is improved, but oxidation occurs leading to increased contact resistance
Solution Approach 1:
The patent removes the cobalt oxidation layer through selective etching processes, extracting the harmful oxidized portion while preserving the conductive cobalt core. This is achieved by etching the liner layer and oxidation layer to expose fresh cobalt surface, thereby eliminating the high-resistance oxide barrier.
Solution Approach 2:
The patent employs an inert atmosphere during deposition and processing to prevent cobalt oxidation. By maintaining a nitrogen or vacuum environment during critical fabrication steps, the cobalt contact remains protected from atmospheric oxygen, preventing oxidation before it can occur.
2Productivity
If technology nodes are scaled to smaller dimensions, then device density is improved, but contact resistance increases due to oxidation
Solution Approach 1:
The patent performs preliminary protective actions by depositing liner layers (such as titanium nitride or tantalum) on the cobalt contact before oxidation can occur. These liner layers serve as protective barriers that prevent oxidation during subsequent processing steps, ensuring low contact resistance is maintained throughout fabrication.
Solution Approach 2:
The patent changes the physical and chemical parameters of the contact structure by introducing multi-layer compositions (cobalt core with protective liners) and controlling deposition parameters. This allows the contact to maintain low resistance despite scaling, as the liner layers prevent oxidation even at smaller dimensions.
3Area of stationary object
If liner layer is removed to expose cobalt core, then contact area is increased, but cobalt oxidation is exposed
Solution Approach 1:
The patent introduces an intermediary protective layer (such as titanium nitride or tantalum liner) that sits between the cobalt core and the oxidizing environment. This intermediary layer allows the cobalt contact area to be maximized while simultaneously protecting the cobalt from oxidation, solving both requirements.
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 results in reduced contact resistance and improved performance of cobalt interconnects by increasing the contact area and eliminating cobalt oxidation layers, thereby enhancing the efficiency of cobalt interconnects in semiconductor devices.
Implementation Method 1
depositing a metal on the liner layer to form an interconnect structure
Data Source
AI summary
A method of fabricating features of a semiconductor device includes forming a contact over a substrate, the contact including a cobalt core and a liner layer arranged on sidewalls, wherein the contact includes a portion that is laterally surrounded by an interlevel dielectric (ILD); depositing another layer of ILD on the contact; etching a first opening in the ILD to expose a surface of the contact; removing the liner layer of the contact to expose a portion of the cobalt core; etching the ILD that laterally surrounds the contact to form a second opening beneath the first opening, the second opening having a width that is less than the first opening; depositing a liner on sidewalls of the first opening, the second opening, and directly on the cobalt core; and depositing a metal on the liner layer to form an interconnect structure.