CuMn-Ta Metal Oxide Diffusion Barrier for Copper Interconnects
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Solution Overview
Problem
Current diffusion barrier layers in copper interconnects, such as those made from refractory metals, exhibit high resistance and poor adhesion to low-k dielectric materials, leading to increased RC delay and yield issues in semiconductor devices, especially in advanced scales and small features.
Innovation Solution
A method involving the formation of a self-aligned diffusion barrier layer using a copper-manganese (CuMn) layer with a subsequent α-phase tantalum (α-Ta) barrier layer, followed by a thermal treatment to form a metal oxide diffusion barrier layer, which reduces contact resistance and prevents copper diffusion into the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refractory metals (Ta, Ti) or nitride compounds are used as diffusion barrier layer materials, then copper diffusion prevention is achieved, but resistance increases and RC delay worsens
Solution Approach 1:
The patent uses a composite barrier layer structure consisting of a first barrier layer (e.g., Ta, Ti, or their nitrides) deposited on the IMD layer, followed by a second barrier layer (e.g., CuMn alloy) deposited on the first barrier layer. This composite structure combines the strong diffusion blocking capability of refractory metals with the low resistance properties of the CuMn alloy, achieving both copper diffusion prevention and low resistance.
Solution Approach 2:
The patent applies different materials with different properties at different locations within the barrier layer structure. The first barrier layer (refractory metal) provides strong diffusion blocking at the interface with the IMD layer, while the second barrier layer (CuMn alloy) provides low resistance in the region adjacent to the copper interconnect, optimizing both diffusion prevention and electrical performance locally.
2Reliability
If refractory metals are used as diffusion barrier layer, then diffusion barrier function is achieved, but adhesion to low-k dielectric material deteriorates
Solution Approach 1:
The patent introduces a CuMn alloy layer as an intermediary between the refractory metal barrier layer and the copper interconnect. This intermediate layer improves adhesion to the low-k dielectric material while maintaining the diffusion barrier function of the underlying refractory metal layer, effectively mediating the adhesion problem between refractory metals and low-k materials.
Solution Approach 2:
The composite barrier layer structure combines materials with different adhesion properties. The CuMn alloy layer provides superior adhesion to low-k dielectric materials compared to pure refractory metals, while the underlying refractory metal layer maintains strong diffusion blocking capability, achieving both adhesion and barrier functions through material composition.
3Loss of energy
If barrier layer thickness is reduced to meet scaling requirements, then RC delay is reduced, but adhesion and barrier effectiveness worsen
Solution Approach 1:
The patent employs a composite barrier layer structure where two different materials work synergistically. The first barrier layer (refractory metal) provides strong diffusion blocking even at thin thicknesses, while the second barrier layer (CuMn alloy) provides low resistance and improved adhesion. This composite approach maintains barrier effectiveness and adhesion while enabling thinner overall barrier layer thickness to reduce RC delay.
Solution Approach 2:
The patent optimizes the barrier layer structure by placing different materials in specific positions. The refractory metal layer is positioned at the critical interface with the IMD layer where diffusion blocking is most needed, while the CuMn alloy layer is positioned adjacent to the copper interconnect where low resistance and adhesion are most important. This local optimization allows thin overall thickness while maintaining effectiveness.
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 achieves low resistivity and improved adhesion, reducing RC delay and enhancing yield by forming a low-resistance diffusion barrier layer that prevents copper diffusion into the dielectric layer, thereby improving semiconductor device performance and package capabilities.
Implementation Method 1
a thermal treatment to form a metal oxide diffusion barrier layer
Data Source
AI summary
A device including a dielectric layer overlying a substrate, a conductive line with a sidewall in the dielectric layer, a Ta layer adjoining the sidewall of the conductive line, and a metal oxide formed between the Ta layer and the dielectric layer.