Ru Contact Plug Structure for Low-Resistance MOL Interconnects
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Solution Overview
Problem
In the manufacturing of integrated circuits, the formation of conductive interconnects during middle-of-the-line (MOL) processes faces challenges such as high contact resistance, void formation, and increased reliability issues due to oxidation of metal liners and barrier layers in ambient environments.
Innovation Solution
The implementation of a ruthenium contact structure with a ruthenium oxide intermixing barrier layer formed through an annealing process, which acts as a glue and barrier layer to reduce contact resistance, prevent void formation, and enhance adhesive performance, thereby eliminating the need for additional glue or barrier layers and ion implantation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metal liners and barrier layers are used in MOL processes, then adhesion and diffusion prevention are achieved, but oxidation occurs in ambient environments leading to increased contact resistance and reliability issues
Solution Approach 1:
The ruthenium layer performs multiple functions simultaneously: it serves as the conductive interconnect material, forms a protective oxide barrier layer in situ through annealing, and eliminates the need for separate metal liner and barrier layer depositions. The self-formed ruthenium oxide provides adhesion and diffusion prevention without being susceptible to ambient oxidation like traditional materials.
Solution Approach 2:
The invention uses a composite structure of ruthenium metal and ruthenium oxide formed through controlled annealing. The ruthenium provides electrical conductivity while the ruthenium oxide forms a protective and adhesive interface with the dielectric layer, creating a composite material system that combines conductive and protective functions.
2Reliability
If additional glue layers and barrier layers are deposited to prevent oxidation and improve adhesion, then reliability improves, but manufacturing complexity and process steps increase
Solution Approach 1:
The ruthenium layer is designed to perform multiple functions that traditionally required separate layers: it provides the conductive interconnect function, forms the diffusion barrier, and creates the adhesive interface with the dielectric through in-situ oxide formation. This multi-functional approach eliminates the need for separate metal liner, barrier layer, and glue layer depositions.
Solution Approach 2:
The invention merges the functions of the metal liner, barrier layer, and adhesive layer into a single ruthenium layer that undergoes controlled oxidation during annealing. The ruthenium and its oxide coexist in a composite structure that provides all necessary functions, reducing the overall layer stack and process complexity.
3Temperature
If ruthenium is used as the conductive interconnect material, then tolerance for subsequent manufacturing processes improves due to high melting point, but additional annealing process is required to form the intermixing barrier layer
Solution Approach 1:
The invention utilizes the phase transition of ruthenium from metallic state to oxidized state through controlled annealing. This phase transition forms the protective and adhesive ruthenium oxide layer in situ, leveraging the material's thermal stability and high melting point to withstand the annealing process without compromising the interconnect structure.
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 solution reduces contact resistance, improves reliability by preventing void formation, and simplifies the manufacturing process by eliminating the need for additional deposition and ion implantation steps, while maintaining high tolerance for subsequent manufacturing processes due to ruthenium's high melting point.
Implementation Method 1
an annealing process to form an intermixing barrier layer at an interface of the plurality of conductive plugs and the upper dielectric layer
Implementation Method 2
acts as a glue and barrier layer to reduce contact resistance, prevent void formation, and enhance adhesive performance
Data Source
AI summary
In some embodiments, the present disclosure relates to an integrated circuit device. A transistor structure includes a gate electrode separated from a substrate by a gate dielectric and a pair of source/drain regions disposed within the substrate on opposite sides of the gate electrode. A lower conductive plug is disposed through a lower inter-layer dielectric (ILD) layer and contacting a first source/drain region. A capping layer is disposed directly on the lower conductive plug. An upper inter-layer dielectric (ILD) layer is disposed over the capping layer and the lower ILD layer. An upper conductive plug is disposed through the upper ILD layer and directly on the capping layer.