Composite Ta/TaN Barrier Layers for Cu Interconnects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor devices face challenges in forming reliable, low resistance Cu or Cu alloy interconnects, particularly in low dielectric constant materials, due to adhesion issues with tantalum (Ta) and tantalum nitride (TaN) barrier layers, which impact electromigration resistance and circuit speed.
Innovation Solution
A composite barrier layer comprising a layer of α-tantalum (α-Ta) over a tantalum nitride (TaN) layer is formed, with controlled surface roughness, to improve adhesion and reduce Cu diffusion, thereby enhancing electromigration resistance and device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional Ta or TaN barrier layer is used to prevent Cu diffusion, then Cu diffusion is reduced, but adhesion between the barrier layer and Cu interconnect deteriorates
Solution Approach 1:
The patent employs a composite barrier layer structure consisting of multiple layers including Ta, TaN, and TiN deposited in sequence. This composite structure combines the Cu diffusion barrier properties of Ta and TaN with the superior adhesion characteristics of TiN, thereby simultaneously achieving both Cu diffusion prevention and strong adhesion to Cu interconnects.
Solution Approach 2:
The TiN layer serves as an intermediary between the Ta/TaN barrier layers and the Cu interconnect. This intermediate layer improves adhesion by providing a transition interface that bonds well with both the barrier layer above and the Cu metal below, while the Ta and TaN layers continue to provide the primary Cu diffusion barrier function.
2Ease of manufacture
If a smooth barrier layer interface is formed, then Cu deposition is facilitated, but Cu diffusion along the interface increases
Solution Approach 1:
The patent applies different surface roughness characteristics to different regions of the barrier layer interface. By controlling the deposition process to create localized roughness features at the Cu/barrier layer interface, the structure prevents Cu diffusion pathways while still allowing complete Cu deposition coverage through subsequent CMP processing.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the barrier layer interface by controlling deposition conditions to achieve specific surface roughness values. This parameter control creates an interface morphology that blocks Cu diffusion paths while maintaining compatibility with Cu deposition and subsequent planarization processes.
3Object-generated harmful factors
If the barrier layer thickness is increased to prevent Cu diffusion, then Cu diffusion is reduced, but contact resistance increases
Solution Approach 1:
The patent uses a composite multi-layer barrier structure where each layer contributes differently to the overall function. The combined thickness of Ta, TaN, and TiN layers provides effective Cu diffusion blocking equivalent to or greater than a single thick layer, while the optimized total thickness and material composition maintain low contact resistance by ensuring good adhesion and electrical contact.
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 solution significantly reduces Cu diffusion along the Cu/barrier layer interface, improves adhesion, and prevents shadowing during subsequent Cu deposition, resulting in enhanced electromigration resistance and device reliability, while maintaining low contact resistance.
Implementation Method 1
A composite barrier layer comprising a layer of α-tantalum (α-Ta) over a tantalum nitride (TaN) layer is formed
Implementation Method 2
The solution significantly reduces Cu diffusion along the Cu/barrier layer interface
Implementation Method 3
improves adhesion
Data Source
AI summary
A composite α-Ta/graded tantalum nitride/TaN barrier layer is formed in Cu interconnects with a controlled surface roughness for improved adhesion, electromigration resistance and reliability. Embodiments include lining a damascene opening, such as a dual damascene opening in a low-k interlayer dielectric, with an initial layer of TaN, forming a graded tantalum nitride layer on the initial TaN layer and then forming an α-Ta layer on the graded TaN layer, the composite barrier layer having an average surface roughness (Ra) of about 25 Å to about 50 Å. Embodiments further include controlling the surface roughness of the composite barrier layer by varying the N2 flow rate and/or ratio of the thickness of the combined α-Ta and graded tantalum nitride layers to the thickness of the initial TaN layer.