Cobalt Barrier Layer Selectivity via Plasma Treatment
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Solution Overview
Problem
In semiconductor manufacturing, particularly for CMOS integrated circuits, there is a need to minimize the amount of cobalt deposited on dielectric layers to reduce leakage current between Cu interconnection lines, as excessive cobalt deposition increases leakage current and affects the reliability of the product.
Innovation Solution
A method involving atomic layer deposition of a dielectric material film on the inter-line dielectric layer to densify its surface, followed by selective cobalt deposition using chemical vapor deposition, with optional reducing plasma treatment to enhance deposition selectivity and reduce cobalt on the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt is deposited to block Cu diffusion and prevent moisture penetration, then adhesion and reliability are improved, but leakage current between Cu interconnection lines increases
Solution Approach 1:
The patent applies different surface treatments to different regions: metal interconnection lines receive reducing plasma treatment to enhance cobalt deposition, while porous dielectric layers maintain their original state to minimize cobalt deposition. This local differentiation allows cobalt to be selectively deposited where needed (on metal lines for adhesion and diffusion barrier) while avoiding excessive deposition on dielectric layers that would cause leakage current.
Solution Approach 2:
The patent changes the surface chemical state parameter by applying reducing plasma treatment to metal interconnection lines before cobalt deposition. This alters the surface properties of metal lines to promote cobalt deposition while the porous dielectric layer retains its original surface properties, creating a parameter difference that enables selective cobalt deposition and reduces leakage current.
2Reliability
If a porous low-k dielectric material is used to reduce RC delay, then dielectric constant is reduced to 2.5 or less, but surface porosity increases cobalt deposition and leakage current
Solution Approach 1:
The patent treats different surfaces differently: metal interconnection lines undergo reducing plasma treatment to become cobalt-attracting, while porous dielectric layers are left untreated to maintain low cobalt deposition. This local quality differentiation exploits the inherent porosity of the dielectric material without attempting to modify it, thereby minimizing cobalt deposition on dielectric surfaces while still achieving the desired RC delay reduction.
Solution Approach 2:
The patent introduces reducing plasma treatment as an intermediary process that selectively modifies only the metal interconnection line surfaces before cobalt deposition. This intermediary treatment creates a chemical distinction between metal lines and dielectric layers, causing cobalt to preferentially deposit on treated metal surfaces while avoiding untreated porous dielectric surfaces, thus reducing leakage current.
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 improves cobalt deposition selectivity, reducing leakage current and enhancing the yield and reliability of the product by selectively depositing cobalt on metal interconnection lines while minimizing its presence on the dielectric layer.
Implementation Method 1
depositing a dielectric material film on a surface of the inter-line dielectric layer by atomic layer deposition, to densify the surface of the inter-line dielectric layer
Implementation Method 2
treating the surfaces of the metal interconnection lines and the surface of the inter-line dielectric layer with reducing plasma treatment
Implementation Method 3
selectively depositing cobalt on surfaces of the metal interconnection lines to form a cobalt barrier layer
Data Source
AI summary
The present invention provides a method for forming a cobalt barrier layer and a metal interconnection process. The method is performed on a surface of a semiconductor device substrate on which metal interconnection lines and an inter-line dielectric layer are formed, and comprises: depositing a dielectric material film on a surface of the inter-line dielectric layer by atomic layer deposition, to densify the surface of the inter-line dielectric layer; removing the deposited dielectric material film, to expose the metal interconnection lines and the densified surface of the inter-line dielectric layer; selectively depositing cobalt on surfaces of the metal interconnection lines to form a cobalt barrier layer. In the present invention, deposition selectivity of cobalt on surfaces of the metal interconnection lines and the inter-line dielectric layer is improved, thus reducing leakage current between metal interconnection lines and improving yield and reliability of the product.