Disconnected Liner Interconnect Structure for Electromigration Resistance
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Solution Overview
Problem
In the back-end-of-line (BEOL) semiconductor fabrication, the narrow interconnect lines are susceptible to electromigration, leading to issues such as delamination and metal extrusion due to the diffusion of cobalt into the ruthenium liner, which affects the reliability of copper interconnects, especially at pitches below 30 nanometers.
Innovation Solution
The implementation of a disconnected liner and metal cap structure prevents the diffusion of metal from the cap into the liner by using a spacer layer and a dielectric cap, ensuring stable copper interconnects and reducing electromigration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt is used in the interconnect structure, then the electrical conductivity is improved, but metal diffusion occurs leading to delamination and metal extrusion
Solution Approach 1:
The interconnect structure is segmented into distinct functional layers: a cobalt cap layer for electrical conductivity, a ruthenium liner layer for diffusion barrier properties, and a titanium nitride diffusion barrier layer. This segmentation allows each material to perform its optimal function without causing harmful diffusion effects.
Solution Approach 2:
The ruthenium liner layer acts as an intermediary between the cobalt cap and the copper interconnect. It prevents direct contact and diffusion between cobalt and copper, while also providing a suitable surface for copper deposition. The titanium nitride layer serves as an additional intermediary diffusion barrier.
2Productivity
If the pitch is reduced below 30 nanometers, then the device density is improved, but electromigration susceptibility increases
Solution Approach 1:
The interconnect structure uses a composite material system consisting of multiple layers with complementary properties: cobalt provides electrical conductivity, ruthenium provides diffusion barrier properties and electromigration resistance, and titanium nitride provides additional diffusion barrier protection. This composite structure maintains reliability at reduced pitches below 30 nanometers.
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 enhances the reliability and performance of copper interconnects by preventing metal diffusion, thereby improving the electromigration resistance and maintaining void-free interconnects even at smaller pitches.
Implementation Method 1
a diffusion barrier layer disposed on exterior surfaces of an opening in a dielectric layer
Implementation Method 2
a spacer layer disposed on the top surface of the diffusion barrier layer and the liner layer and exposed sidewalls of the opening
Data Source
AI summary
An interconnect structure includes a diffusion barrier layer disposed on exterior surfaces of an opening in a dielectric layer. A top surface of the diffusion barrier layer is below a top surface of the opening. A liner layer is disposed on a bottom surface and sidewalls of the diffusion barrier layer. A spacer layer is disposed on the top surface of the diffusion barrier layer and the liner layer and exposed sidewalls of the opening. An interconnect metal is disposed on the liner layer and the spacer layer. A metal cap is disposed on the interconnect metal.