Cobalt Contact Silicide Capping for Oxidation and Migration Control
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Solution Overview
Problem
Cobalt-based interconnects in semiconductor devices are prone to oxidation and migration, leading to increased contact resistance and electrical shorts, which are not effectively inhibited by existing dielectric capping materials.
Innovation Solution
A self-aligned cobalt silicide capping layer is formed by depositing a thin silicon layer over cobalt contacts and reacting it with cobalt through heat treatment, creating a barrier against oxidation and migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt contacts are used to reduce electromigration, then reliability is improved, but oxidation and migration during processing increase contact resistance and cause electrical shorts
Solution Approach 1:
A silicon capping layer is deposited over the cobalt contact to act as an intermediary barrier. This silicon layer prevents direct exposure of cobalt to oxidizing environments during subsequent processing steps, thereby inhibiting cobalt oxidation and migration while maintaining the electromigration resistance benefits of cobalt
Solution Approach 2:
The silicon capping layer creates an inert protective environment over the cobalt contact. By forming a stable silicon-rich surface layer through thermal treatment, the cobalt is isolated from reactive oxygen species in the processing environment, effectively creating a protective atmosphere that prevents oxidation and migration
2Object-affected harmful factors
If dielectric capping layers are used to protect cobalt contacts, then oxidation is partially inhibited, but cobalt migration to adjacent regions still occurs
Solution Approach 1:
The silicon capping layer serves as a direct intermediary contact with the cobalt surface, forming a silicon-rich barrier layer that simultaneously addresses both oxidation and migration issues. Unlike dielectric layers that only partially protect, the silicon layer creates a stable interface that prevents cobalt atoms from migrating to adjacent regions
3Manufacturing precision
If thin barrier layer architectures are used to meet resistance requirements, then device performance is improved, but cobalt migration becomes more problematic
Solution Approach 1:
The silicon capping layer provides a robust barrier against cobalt migration that is independent of the underlying barrier layer thickness. By depositing silicon directly over the cobalt contact and forming a silicon-rich surface layer, it creates a migration barrier that remains effective even when the barrier layer architecture is scaled down to meet resistance requirements at advanced nodes
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
The cobalt silicide capping layer effectively prevents cobalt oxidation and migration, maintaining device performance and reliability by reducing contact resistance and preventing electrical shorts.
Implementation Method 1
reacting the deposited silicon with the cobalt to form a cobalt silicide
Implementation Method 2
The cobalt silicide is an effective barrier to cobalt migration and oxidation
Implementation Method 3
followed by heat treatment to react the deposited silicon with the cobalt and form a cobalt silicide
Data Source
AI summary
A process for forming a conductive structure includes the formation of a self-aligned silicide cap over a cobalt-based contact. The silicide cap is formed in situ by the deposition of a thin silicon layer over exposed portions of a cobalt contact, followed by heat treatment to react the deposited silicon with the cobalt and form cobalt silicide, which is an effective barrier to cobalt migration and oxidation.