Nitrogen Gradient Barrier Layer for Copper Interconnect Adhesion
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Solution Overview
Problem
In integrated circuits, the challenge is to deposit a thin and conformal barrier layer that provides good adhesion to both the dielectric layer and the copper layer, while maintaining step coverage and preventing electro-migration and stress-induced voiding, especially in 45-nm-node or sub-45-nm technology where conventional methods fail due to poor adhesion and step coverage issues.
Innovation Solution
A method using atomic layer deposition (ALD) to create a barrier layer with decreasing nitrogen concentration as the film thickness increases, ensuring high nitrogen concentration at the dielectric interface for strong adhesion and low nitrogen concentration at the copper interface for improved adhesion, thereby enhancing the barrier layer's conformality and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thin and conformal barrier layer is deposited to reduce impact on via and line resistance, then the barrier's impact on resistance is reduced, but adhesion between copper and barrier layer becomes poor causing delamination
Solution Approach 1:
The barrier layer is designed with varying nitrogen concentration through its thickness: high nitrogen concentration at the bottom interface with dielectric for strong adhesion, and low nitrogen concentration at the top interface with copper for improved copper adhesion. This gradient composition allows each region of the barrier layer to have optimized properties for its specific function.
Solution Approach 2:
The nitrogen concentration parameter is continuously varied through the barrier layer thickness during deposition. By controlling the nitrogen flow rate or precursor ratios during atomic layer deposition, the composition transitions from nitrogen-rich at the bottom to nitrogen-poor at the top, enabling simultaneous optimization of adhesion to both dielectric and copper layers.
2Reliability
If a two-step barrier process with TaN layer followed by Ta layer is used to improve copper adhesion, then copper adhesion is improved, but the aspect ratio of interconnect structure increases worsening step coverage
Solution Approach 1:
The functions of multiple barrier layers (TaN for dielectric adhesion and Ta for copper adhesion) are merged into a single gradient-composition barrier layer. By varying nitrogen concentration continuously through the thickness, one layer performs both adhesion functions simultaneously, avoiding the need for additional deposition steps that would increase aspect ratio and worsen step coverage.
Solution Approach 2:
The barrier layer is created as a composite structure with varying composition (nitrogen concentration gradient) rather than a homogeneous material. This composite approach allows different regions of the same layer to provide different functions (dielectric adhesion at bottom, copper adhesion at top), eliminating the need for separate functional layers.
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 results in improved adhesion between the barrier layer and both the dielectric and copper layers, reducing the risk of electro-migration and stress-induced voiding, and enhances the overall yield and performance of copper interconnects.
Implementation Method 1
depositing a barrier layer with a first nitrogen concentration during a first phase of deposition in the atomic layer deposition environment
Data Source
AI summary
Various embodiments provide improved processes and systems that produce a barrier layer with decreasing nitrogen concentration with the increase of film thickness. A barrier layer with decreasing nitrogen concentration with film thickness allows the end of barrier layer with high nitrogen concentration to have good adhesion with a dielectric layer and the end of barrier layer with low nitrogen concentration (or metal-rich) to have good adhesion with copper. An exemplary method of depositing a barrier layer on an interconnect structure is provided. The method includes (a) providing an atomic layer deposition environment, (b) depositing a barrier layer on the interconnect structure with a first nitrogen concentration during a first phase of deposition in the atomic layer deposition environment. The method further includes (c) continuing the deposition of the barrier layer on the interconnect structure with a second nitrogen concentration during a second phase deposition in the atomic layer deposition environment.