Cobalt Interconnects via Plasma Surface Treatment
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Solution Overview
Problem
The semiconductor industry faces challenges in forming compact low-resistance contacts to FinFETs to maintain high current conduction capability while maintaining a small planar footprint, as conventional methods struggle with reducing the presence of thin oxide layers that impede current flow in conductive interconnects, especially at ultra-small cross-sectional areas.
Innovation Solution
The use of cobalt as a principal conductive material and surface preparation processes, including reactive remote plasma surface treatment and in-situ wet surface treatment, to deposit cobalt and reduce or eliminate the cobalt oxide layer, thereby enhancing the conductance of interconnect structures and improving the efficiency of current access to electronic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition methods are used to form conductive interconnect structures, then the manufacturing process is simple, but thin oxide layers form on the conductive material surface which impede current flow and increase resistance
Solution Approach 1:
The patent applies preliminary surface treatment actions (plasma treatment, chemical etching, or mechanical polishing) to the conductive material surface before final deposition to prevent oxide layer formation. This preliminary action removes surface contaminants and creates a surface state that resists oxidation, thereby maintaining low resistance without requiring complex post-processing steps.
Solution Approach 2:
The patent converts the harmful oxide layer formation into a beneficial process by using controlled oxidation followed by reduction. The surface is intentionally oxidized and then treated with reducing agents or plasma to remove the oxide, leaving a clean, oxide-resistant surface. This converts the natural tendency toward oxidation from a harmful effect into a controlled process that ensures surface quality.
2Area of stationary object
If the cross-sectional area of conductive interconnects is reduced to maintain small planar footprint, then the device density increases, but the current conduction capability decreases due to higher resistance
Solution Approach 1:
The patent changes the surface properties of the conductive material through plasma treatment, chemical modification, or surface coating to reduce contact resistance. By modifying surface parameters (roughness, chemistry, conductivity) rather than changing the bulk dimensions, the patent maintains low resistance in ultra-small cross-sectional areas, enabling continued scaling without sacrificing current conduction capability.
3Reliability
If cobalt is used as conductive material to improve conductance, then the electrical performance improves, but cobalt oxide formation on the surface increases resistance
Solution Approach 1:
The patent introduces an intermediary layer or treatment (such as a protective coating, surface passivation layer, or plasma treatment) between the cobalt conductive material and the oxidizing environment. This intermediary prevents direct oxidation of the cobalt surface while maintaining electrical conductivity, effectively decoupling the beneficial bulk conductance of cobalt from the harmful surface oxidation effect.
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 the time required to electrically access electronic devices, improves the performance of electrical circuits, and enables the miniaturization of integrated circuits by enhancing the conductance of interconnect structures, particularly at small dimensions, leading to higher packing density and production yields.
Implementation Method 1
depositing a conductive layer over the conductive seed layer in the opening
Implementation Method 2
electroplating a conductive layer over the conductive seed layer
Implementation Method 3
surface preparation processes, including reactive remote plasma surface treatment and in-situ wet surface treatment, to deposit cobalt and reduce or eliminate the cobalt oxide layer
Data Source
AI summary
An interconnect structure and a method of forming the interconnect structure are provided. A dielectric layer and openings therein are formed over a substrate. A conductive seed layer is formed over the top surface and along a bottom and sidewalls of the openings. A conductive fill layer is formed over the seed layer. Metal oxide on the surface of the seed layer may be reduced/removed by a surface pre-treatment. The cleaned surface is covered by depositing fill material over the seed layer without exposing the surface to oxygen. The surface treatment may include a reactive remote plasma clean using hydrogen radicals. If electroplating is used to deposit the fill layer, then the surface treatment may include soaking the substrate in the electrolyte before turning on the electroplating current. Other surface treatments may include active pre-clean (APC) using hydrogen radicals; or Ar sputtering using a metal clean version xT (MCxT) tool.