Selective Metal Cap Interconnects for Low-Resistivity Interfaces
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Solution Overview
Problem
The reduction in size of active and passive devices has complicated the formation and structure of interconnects, leading to increased oxidation at interfaces, which causes high resistivity and damage to sidewalls during plasma cleaning, affecting the performance of subsequently deposited barrier layers.
Innovation Solution
A selective deposition of a metal cap is performed on conductive features followed by a barrier layer and conductive fill, without breaking vacuum, to minimize oxidation and enhance conductivity at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device size is reduced to improve integration density, then productivity and miniaturization are improved, but oxidation at interfaces increases causing high resistivity
Solution Approach 1:
A metal cap layer is deposited on the conductive feature surface before the barrier layer is formed. This preliminary action creates a protective interface that prevents oxidation between the conductive feature and barrier layer, solving the resistivity issue that arises from device miniaturization.
Solution Approach 2:
The metal cap acts as an intermediary layer between the conductive feature and the barrier layer. This intermediate structure prevents direct contact and potential oxidation between the conductive feature and barrier layer, while still allowing electrical connection through the conductive metal cap material.
2Object-affected harmful factors
If plasma cleaning is performed to remove oxidation, then cleanliness is improved, but sidewalls are damaged affecting barrier layer quality
Solution Approach 1:
The metal cap is deposited before the barrier layer formation process. This preliminary deposition creates a protective interface that eliminates the need for aggressive plasma cleaning that would damage sidewalls, while still providing oxidation protection at the critical interface.
Solution Approach 2:
Instead of using plasma cleaning to remove oxidation (which causes sidewall damage), the invention converts the approach by using metal cap deposition to prevent oxidation in the first place. The harmful plasma cleaning step is replaced with a beneficial deposition step that protects the interface without damaging sidewalls.
3Device complexity
If conventional deposition processes are used, then process simplicity is maintained, but oxidation at interfaces causes high resistivity
Solution Approach 1:
The deposition process is segmented into distinct steps: first depositing the metal cap layer, then depositing the barrier layer. This segmentation allows for optimized deposition conditions for each layer and ensures proper interface formation without oxidation, improving reliability while adding only one essential process step.
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 and enhances the contact area between metal cap and conductive features, resulting in improved conductivity and reduced defects in interconnects.
Implementation Method 1
A selective deposition of a metal cap is performed on 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 conductive features followed by a barrier layer and conductive fill
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.