Nitridized Ruthenium Adhesion Layer for Cobalt Interconnects
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Solution Overview
Problem
As integrated circuit features shrink, conventional lithography faces challenges in reducing resistance-capacitance (RC) delay due to increased copper resistivity, leading to signal speed issues in densely packed circuits.
Innovation Solution
The use of a ruthenium and cobalt layer combination as interconnect materials, with a nitridized ruthenium layer promoting adhesion and cobalt deposition through physical vapor deposition, to reduce RC delays in aggressively scaled features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as interconnect material in conventional lithography, then manufacturing process is simple, but resistance increases as dimensions shrink leading to increased RC delay
Solution Approach 1:
The patent uses a composite interconnect structure consisting of a ruthenium layer and a cobalt layer. The ruthenium layer provides a diffusion barrier and adhesion promotion, while the cobalt layer provides low resistivity. This composite material approach allows the interconnect to maintain low resistance even as dimensions shrink, overcoming the limitation of conventional copper interconnects where resistance increases with reduced feature size.
2Speed
If feature dimensions are reduced to improve circuit performance, then signal speed should improve, but copper resistivity increases causing increased RC delay
Solution Approach 1:
The patent changes the material parameters of the interconnect by transitioning from copper to a ruthenium-cobalt composite. The cobalt layer has resistivity that remains relatively stable at nanoscale dimensions, unlike copper whose resistivity increases significantly as dimensions shrink. This parameter change in material composition allows the interconnect to maintain low resistance and enable high signal speed in aggressively scaled features.
3Reliability
If ruthenium and cobalt layers are used instead of copper, then RC delay is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent segments the interconnect structure into two distinct functional layers: a ruthenium layer that provides diffusion barrier and adhesion properties, and a cobalt layer that provides low resistivity. This segmentation allows each layer to be optimized for its specific function while together they achieve superior RC delay performance compared to conventional copper interconnects.
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 lower resistance in narrow wires, improving metal fill properties and reliability of interconnects, thereby reducing RC delays and enhancing overall circuit performance.
Implementation Method 1
A nitridized ruthenium layer is disposed over the adhesion promoting layer
Implementation Method 2
A cobalt layer disposed over the nitridized ruthenium layer filling the set of features, wherein the cobalt layer is formed using a physical vapor deposition process
Data Source
AI summary
An advanced metal conductor structure is described. An integrated circuit device including a substrate having a dielectric layer is patterned. The pattern includes a set of features in the dielectric for a set of metal conductor structures. An adhesion promoting layer is disposed over the set of features in the patterned dielectric. A nitridized ruthenium layer is disposed over the adhesion promoting layer. A cobalt layer disposed over the nitridized ruthenium layer filling the set of features, wherein the cobalt layer is formed using a physical vapor deposition process.