Graded Titanium Nitride Diffusion Barrier for Copper Interconnects
Solution Overview
Problem
Conventional tantalum-based diffusion barrier films are not compatible with low-k and ultra-low-k dielectric materials, especially those containing residual moisture, leading to inadequate protection and reliability issues in copper interconnects, while titanium-based diffusion barriers face challenges with titanium diffusion into copper and adhesion problems.
Innovation Solution
A compositionally graded titanium nitride diffusion barrier film with a nitrogen-rich portion and a nitrogen-poor portion is used, along with a Ti/TiOx layer, to provide excellent adhesion and prevent titanium diffusion, suitable for low-k and ultra-low-k dielectric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tantalum-based diffusion barrier films are used, then diffusion barrier protection is provided, but compatibility with low-k and ultra-low-k dielectric materials is poor
Solution Approach 1:
The patent applies local quality by creating a compositionally graded titanium nitride layer where the nitrogen concentration varies through the thickness of the layer. The nitrogen-rich portion (closer to the dielectric) provides excellent diffusion barrier protection, while the nitrogen-poor portion (closer to the copper) ensures good adhesion and compatibility with low-k and ultra-low-k dielectric materials. This spatial variation in composition allows each region to optimize its function for the specific interface it contacts.
Solution Approach 2:
The patent uses composite materials by combining titanium nitride with varying nitrogen concentrations in a single graded layer, rather than using a uniform material. This compositional gradient creates a composite structure that integrates the benefits of both nitrogen-rich (superior barrier) and nitrogen-poor (superior adhesion and compatibility) regions, resolving the contradiction between diffusion barrier protection and compatibility with sensitive dielectric materials.
2Adaptability or versatility
If titanium-based diffusion barriers are used, then compatibility with low-k and ultra-low-k dielectric materials is improved, but titanium diffusion into copper occurs
Solution Approach 1:
The patent applies local quality by creating a compositionally graded titanium nitride layer where the nitrogen concentration varies through the thickness of the layer. The nitrogen-rich portion (closer to the dielectric) provides excellent diffusion barrier protection, while the nitrogen-poor portion (closer to the copper) ensures good adhesion and compatibility with low-k and ultra-low-k dielectric materials. This spatial variation in composition allows each region to optimize its function for the specific interface it contacts.
Solution Approach 2:
The patent uses parameter changes by varying the nitrogen concentration parameter through the thickness of the titanium nitride layer. This compositional gradient transforms the material properties from uniform to non-uniform, allowing the barrier layer to simultaneously provide diffusion protection and adhesion by adjusting the nitrogen content at different positions within the layer.
3Reliability
If stoichiometric or nitrogen-rich titanium nitride is used, then diffusion barrier properties are maintained, but adhesion to copper deteriorates
Solution Approach 1:
The patent applies local quality by creating a compositionally graded titanium nitride layer where the nitrogen concentration varies through the thickness of the layer. The nitrogen-rich portion (closer to the dielectric) provides excellent diffusion barrier protection, while the nitrogen-poor portion (closer to the copper) ensures good adhesion and compatibility with low-k and ultra-low-k dielectric materials. This spatial variation in composition allows each region to optimize its function for the specific interface it contacts.
Solution Approach 2:
The patent applies segmentation by dividing the titanium nitride barrier layer into distinct compositional regions: a nitrogen-rich portion for diffusion barrier functionality and a nitrogen-poor portion for adhesion to copper. This segmentation allows each sub-region to independently optimize its properties for its specific function, resolving the contradiction between maintaining diffusion barrier properties and achieving good adhesion.
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 effectively addresses the compatibility and reliability issues by maintaining the diffusion barrier properties and adhesion to copper, reducing titanium diffusion, and ensuring compatibility with low-k and ultra-low-k dielectric materials.
Implementation Method 1
The diffusion barrier layer protects inter-metal dielectric (IMD) and active devices from diffusion of copper and other readily diffusing metals into these regions
Implementation Method 2
The resulting barrier film provides excellent diffusion barrier properties due to the presence of nitrogen-rich TiNx, exhibits good adhesion at copper interface, due to good adhesion of nitrogen-poor TiNx to copper
Data Source
AI summary
A diffusion barrier film includes a layer of compositionally graded titanium nitride, having a nitrogen-rich portion and a nitrogen-poor portion. The nitrogen-rich portion has a composition of at least about 40% (atomic) N, and resides closer to the dielectric than the nitrogen-poor portion. The nitrogen-poor portion has a composition of less than about 30% (atomic) N (e.g., between about 5-30% N) and resides in contact with the metal, e.g., copper. The diffusion barrier film can also include a layer of titanium residing between the layer of dielectric and the layer of compositionally graded titanium nitride. The layer of titanium is often partially or completely converted to titanium oxide upon contact with a dielectric layer. The barrier film having a compositionally graded titanium nitride layer provides excellent diffusion barrier properties, exhibits good adhesion to copper, and reduces uncontrolled diffusion of titanium into interconnects.