Alternating PVD ALD Diffusion Barrier for Copper Interconnects
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Solution Overview
Problem
Copper diffusion through interlayer dielectric layers in semiconductor devices poses reliability issues as ICs scale down, leading to potential device failure and transistor poisoning, necessitating effective diffusion barriers.
Innovation Solution
A method involving the formation of a diffusion barrier material, such as tantalum nitride, using alternating steps of physical vapor deposition (PVD) and atomic layer deposition (ALD) to create a void-free and defect-free layer over the conductive material, combined with a ruthenium liner layer to prevent copper diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used for metallization lines to improve electrical conductivity and electromigration resistance, then conductivity and reliability are improved, but copper diffusion through ILD layer causes device reliability issues and transistor poisoning
Solution Approach 1:
A diffusion barrier layer comprising alternating layers of tantalum nitride (TaN) and tungsten nitride (WN) is introduced as an intermediary between the copper metallization lines and the ILD layer. This multi-layer barrier structure prevents copper atoms from diffusing into the dielectric material while maintaining electrical conductivity and electromigration resistance of the copper interconnects.
Solution Approach 2:
The diffusion barrier is formed as a composite structure with alternating layers of tantalum nitride and tungsten nitride. This composite material approach combines the advantages of both materials: TaN provides excellent copper diffusion barrier properties while WN contributes to adhesion and additional barrier functionality, creating a more effective composite barrier system than either material alone.
2Area of moving object
If device size is reduced to enable IC scaling, then integration density is improved, but copper diffusion prevention becomes increasingly critical and difficult
Solution Approach 1:
The diffusion barrier is segmented into multiple thin alternating layers of tantalum nitride and tungsten nitride rather than using a single thick layer. This segmented multi-layer structure provides enhanced copper diffusion prevention through multiple barrier interfaces, which is particularly effective in scaled devices where the barrier thickness must be minimized to maintain process control and avoid void formation.
Solution Approach 2:
The invention changes the parameters of the barrier structure by using alternating layers with different material compositions and thicknesses. The TaN and WN layers have different deposition rates, diffusion barriers, and mechanical properties, allowing optimization of the barrier performance for scaled dimensions while maintaining conformal coverage and preventing copper migration in high-density interconnect structures.
3Ease of manufacture
If single deposition process is used for diffusion barrier to simplify manufacturing, then process complexity is reduced, but voids and defects may form in the barrier layer
Solution Approach 1:
The diffusion barrier is formed using periodic alternating deposition of tantalum nitride and tungsten nitride layers through sequential PVD and ALD processes. This periodic multi-step deposition ensures conformal coverage, prevents void formation at interfaces, and creates a more uniform and defect-free barrier structure compared to single-material deposition, while maintaining manufacturability through standardized semiconductor fabrication 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 solution effectively prevents copper diffusion, ensuring reliable semiconductor devices by forming a robust and uniform diffusion barrier and liner structure, enhancing the reliability of metallization lines in semiconductor interconnects.
Implementation Method 1
The diffusion barrier material is formed over the conductive material by a process of physical vapor deposition (PVD)
Implementation Method 2
The diffusion barrier material is formed over the conductive material by at least two alternating steps selected from the group consisting of a process of physical vapor deposition (PVD) and a process of atomic layer deposition (ALD)
Data Source
AI summary
In a method of fabricating a semiconductor device, an opening is formed inside a dielectric layer above a semiconductor substrate. The opening has a wall. At least one diffusion barrier material is then formed over the wall of the opening by at least two alternating steps, which are selected from the group consisting of a process of physical vapor deposition (PVD) and a process of atomic layer deposition (ALD). A liner layer is formed over the at least one diffusion barrier material.