Selective Metal Cap Interconnects for Low-Resistivity Contacts
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Solution Overview
Problem
The reduction in size of semiconductor devices has led to increased oxidation at the interfaces of metal structures, causing higher resistivity in interconnects, which conventional pre-clean processes fail to adequately address, and plasma-assisted pre-clean methods can damage sidewalls.
Innovation Solution
A selective deposition of a metal cap is performed on the conductive features followed by a barrier layer and conductive fill, without breaking vacuum, to minimize oxidation and enhance conductivity at the interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pre-clean processes are used to remove oxidation at metal interfaces, then oxidation is reduced, but the cleaning effectiveness is insufficient leading to high resistivity in scaled-down interconnects
Solution Approach 1:
A metal cap layer is deposited on the conductive feature surface before the main barrier layer is formed. This preliminary metal cap layer serves as a fresh metal surface that is then cleaned in-situ, ensuring optimal interface quality without requiring extensive pre-cleaning of the underlying conductive feature
Solution Approach 2:
The metal cap layer acts as an intermediary between the conductive feature and the barrier layer. It provides a controlled interface where oxidation can be managed through in-situ cleaning processes, mediating the interaction between the conductive feature and subsequent layers
2Manufacturing precision
If plasma-assisted pre-clean methods are used to remove oxidation, then oxidation removal is improved, but sidewalls of openings become damaged
Solution Approach 1:
The metal cap layer serves as a sacrificial intermediary that absorbs the cleaning process effects. The in-situ cleaning is performed on the metal cap surface rather than directly on the conductive feature sidewalls, protecting the sidewalls from damage while still achieving effective oxidation removal at the interface
Solution Approach 2:
The metal cap is deposited beforehand to create a dedicated surface for cleaning operations. This preliminary structure allows aggressive cleaning methods to be applied selectively to the cap surface without affecting the underlying conductive feature or surrounding sidewalls
3Productivity
If device size is reduced to improve integration, then device density increases, but oxidation at metal interfaces increases causing higher resistivity
Solution Approach 1:
The approach changes the physical state and composition of the metal interface by depositing a fresh metal cap layer. This alters the interface parameters (surface freshness, oxidation state) to achieve lower resistivity despite the reduced dimensions and increased density of the overall device structure
Solution Approach 2:
The interconnect structure becomes composite with multiple metal layers (conductive feature, metal cap) and barrier layers. This composite structure allows optimization of each layer's properties to achieve low resistivity at interfaces while maintaining small overall device dimensions
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 resistivity by enlarging the contact area and minimizing oxidation, resulting in better conductivity and reduced defects in the interconnects.
Implementation Method 1
A selective deposition of a metal cap is performed on the conductive features followed by a barrier layer and conductive fill, without breaking vacuum
Implementation Method 2
A selective deposition of a metal cap is performed on the conductive features followed by a barrier layer and conductive fill, without breaking vacuum
Data Source
AI summary
Embodiments provide a method and resulting structure that includes forming an opening in a dielectric layer to expose a metal feature, selectively depositing a metal cap on the metal feature, depositing a barrier layer over the metal cap, and depositing a conductive fill on the barrier layer.