ALD Cobalt Interconnect Barrier Layer Void Reduction
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Solution Overview
Problem
Copper-based interconnect structures in integrated circuits degrade performance due to voids and increased resistance-capacitance delay as technology advances to smaller nodes, necessitating improved materials and deposition methods for cobalt-based interconnects.
Innovation Solution
A two-step atomic layer deposition (ALD) process forms a conformal and continuous titanium-and-nitrogen containing barrier layer, enhancing adhesion of the cobalt bulk layer and reducing voids, thereby preserving electromigration performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copper-based interconnect structures are used, then manufacturing cost is reduced, but voids form and resistance-capacitance delay increases
Solution Approach 1:
The patent changes the material parameter from copper to cobalt-based interconnect structures. This material substitution resolves the contradiction by providing both void-free morphology and improved electromigration performance while maintaining manufacturing feasibility through established deposition techniques
Solution Approach 2:
The patent employs composite material structures including cobalt bulk layers combined with titanium nitride barrier layers and nitrogen-containing dielectric layers. This composite approach optimizes both electrical performance and structural integrity, eliminating voids while maintaining manufacturability
2Reliability
If cobalt-based interconnect structures are implemented, then electromigration performance is improved, but adhesion of cobalt bulk layer deteriorates due to voids
Solution Approach 1:
The patent introduces nitrogen-containing dielectric layers and titanium nitride barrier layers as intermediary materials between the cobalt bulk layer and substrate. These intermediary layers improve adhesion by providing chemically stable interfaces, eliminating void formation while preserving the superior electromigration performance of cobalt
Solution Approach 2:
The patent modifies the deposition process parameters to achieve conformal coverage and controlled thickness of barrier and dielectric layers. This precise parameter control ensures continuous, void-free structures that maintain strong adhesion while preserving cobalt's electromigration resistance
3Device complexity
If conventional deposition methods are used, then process complexity is reduced, but conformality and continuity of barrier layer deteriorate
Solution Approach 1:
The patent segments the deposition process into multiple sequential steps: forming nitrogen-containing dielectric layers, depositing titanium nitride barrier layers, and depositing cobalt bulk layers. This segmentation enables precise control of each layer's properties, achieving conformal and continuous structures while managing process complexity through systematic breakdown of operations
Solution Approach 2:
The patent employs periodic deposition cycles with alternating precursor exposure and purge steps to achieve atomic-layer precision. This periodic action ensures conformal coverage and continuous layer formation, maintaining manufacturing precision through rhythmically controlled chemical vapor deposition processes
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 ALD-based process improves adhesion and reduces voids in cobalt bulk layers, maintaining electromigration performance and overall IC device performance.
Implementation Method 1
A two-step atomic layer deposition (ALD) process forms a conformal and continuous titanium-and-nitrogen containing barrier layer
Implementation Method 2
performing an ALD-like nitrogen-containing plasma pre-treatment process on the sidewalls of the contact opening
Data Source
AI summary
Interconnect structures and corresponding techniques for forming the interconnect structures are disclosed herein. An exemplary method includes forming a contact opening in a dielectric layer. The contact opening has sidewalls defined by the dielectric layer and a bottom defined by a conductive feature. An ALD-like nitrogen-containing plasma pre-treatment process is performed on the sidewalls (and, in some implementations, the bottom) of the contact opening. An ALD process is performed to form a titanium-and-nitrogen containing barrier layer over the sidewalls and the bottom of the contact opening. A cobalt-containing bulk layer is then formed over the titanium-and-nitrogen-containing barrier layer. A cycle of the ALD-like nitrogen-containing plasma pre-treatment process can include a nitrogen-containing plasma pulse phase and a purge phase. A cycle of the ALD process can include a titanium-containing pulse phase, a first purge phase, a nitrogen-containing plasma pulse phase, and a second purge phase.