Copper Interconnect Adhesion Layer Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of tantalum-based barrier layers in copper interconnects reduces the cross-sectional area of copper, leading to increased copper line resistance as feature sizes diminish, necessitating a solution to enhance copper adhesion and prevent electromigration in low-k dielectric layers.
Innovation Solution
A thin adhesion layer of pure cobalt or ruthenium, deposited using chemical vapor deposition or atomic layer deposition, is applied directly against the low-k dielectric layer surfaces, with a thickness of 10 to 30 Å, to facilitate copper filling and prevent electromigration, while eliminating the need for a barrier layer between copper and the dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tantalum-based barrier layer is used to prevent copper diffusion, then copper diffusion is prevented, but the cross-sectional area of copper is reduced leading to increased copper line resistance
Solution Approach 1:
The patent removes the tantalum barrier layer from the interconnect structure, extracting the source of resistance increase. By eliminating this harmful barrier layer, the copper cross-sectional area is maximized, thereby reducing copper line resistance while alternative methods (nitride layer with openings) are used to prevent copper diffusion.
Solution Approach 2:
The patent changes the material parameter from tantalum barrier layer to silicon nitride layer with controlled openings. This parameter change allows copper to have direct contact with the dielectric in most areas (reducing resistance) while still preventing diffusion through the strategically placed openings in the nitride layer.
2Productivity
If feature sizes are reduced to increase integration density, then integration density is improved, but copper line resistance increases exponentially
Solution Approach 1:
By removing the tantalum barrier layer that occupies significant cross-sectional area, the patent increases the effective copper area even as feature sizes shrink. This extraction of the barrier layer becomes increasingly important at smaller dimensions where the barrier layer would consume a larger proportion of the already reduced feature size.
Solution Approach 2:
The patent applies local quality by creating selective openings in the silicon nitride layer at specific locations (via bottoms and trench ends) where copper diffusion must be prevented, while allowing copper to directly contact the dielectric in all other areas to minimize resistance. This localized approach to barrier application optimizes both diffusion prevention and conductivity.
3Object-affected harmful factors
If a barrier layer is eliminated to increase copper cross-section, then copper line resistance is reduced, but copper diffusion into the dielectric increases
Solution Approach 1:
The patent introduces silicon nitride layer as an intermediary material that replaces the tantalum barrier layer. This nitride layer with controlled openings serves as a new mediator between copper and the dielectric, providing diffusion prevention through the openings while allowing direct copper-dielectric contact in other areas to maintain low resistance.
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 allows for increased copper contact cross-section, improved adhesion, and reduced copper diffusion, maintaining conductivity while simplifying the process by eliminating the need for additional barrier layers, thus addressing the exponential increase in copper line resistance.
Implementation Method 1
A thin adhesion layer of pure cobalt or ruthenium, deposited using chemical vapor deposition or atomic layer deposition
Implementation Method 2
A thin adhesion layer of pure cobalt or ruthenium, deposited using chemical vapor deposition or atomic layer deposition
Data Source
AI summary
A method of filling features in a dielectric layer is provided. A pure Co or pure Ru adhesion layer is deposited against surfaces of the features, wherein the adhesion layer is separated from some of the surfaces of the features of the low-k dielectric layer by no more than 10 Å. The features are filled with Cu or a Cu alloy.