Continuous Ruthenium Film for Void-Free Copper Plating
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Solution Overview
Problem
The challenge in integrated circuit fabrication is the deposition of high-purity continuous ruthenium (Ru) films with low surface roughness for use in copper (Cu) plating of narrow and high-aspect-ratio recessed features, as conventional methods result in poor adhesion and uneven Cu deposition, leading to micro-voids and increased electrical resistivity.
Innovation Solution
A multi-step method involving thermal chemical vapor deposition (TCVD) using a Ru3(CO)12 precursor and carbon monoxide (CO) carrier gas to deposit a substantially oxygen-and carbon-free continuous Ru film, followed by Cu plating and annealing in non-oxidizing gases to form large Cu grains, ensuring void-free filling and reduced resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVD or ALD methods are used to deposit Ru films, then the Ru film can be deposited on dielectric materials, but the Ru film exhibits poor morphology and high surface roughness
Solution Approach 1:
The patent changes the deposition parameters by using thermal chemical vapor deposition (TCVD) with specific temperature control and Ru3(CO)12 precursor, which produces smooth, continuous Ru films with superior morphology compared to conventional CVD or ALD methods
Solution Approach 2:
The patent replaces conventional physical vapor deposition or atomic layer deposition mechanisms with thermal chemical vapor deposition using Ru3(CO)12 precursor decomposition, achieving better film morphology through chemical reaction pathways
2Reliability
If Cu is plated directly onto conventional thin Ru films, then Cu deposition can proceed, but poor adhesion and uneven Cu deposition occur leading to micro-voids
Solution Approach 1:
The patent performs preliminary action by depositing a high-quality continuous Ru film with low surface roughness before Cu plating, which provides an ideal substrate for subsequent Cu deposition and ensures good adhesion and uniformity
Solution Approach 2:
The Ru film acts as an intermediary layer between the dielectric substrate and Cu metal, and the patent optimizes this intermediary by ensuring it is continuous and smooth, which mediates the adhesion and deposition quality of Cu
3Reliability
If post Cu plating annealing is performed to grow large Cu grains, then electrical resistance of Cu material decreases, but narrow and high-aspect-ratio recessed features become increasingly difficult to fill with large grain Cu
Solution Approach 1:
The patent performs preliminary annealing of the Ru film before Cu plating to optimize its morphology and crystalline structure, which facilitates subsequent Cu grain growth and enables large grain formation even in narrow, high-aspect-ratio features
Solution Approach 2:
The patent optimizes annealing parameters (temperature, atmosphere, duration) to control Cu grain growth kinetics, achieving large grains that fill high-aspect-ratio features without voids while maintaining low electrical resistance
4Productivity
If IC dimensions are scaled down to increase device density, then device area decreases and yield increases, but micro-voids in bulk metal filling become unacceptable and electromigration failure increases
Solution Approach 1:
The patent changes the morphology and grain structure parameters of Cu metal through controlled deposition and annealing processes, producing large-grain Cu that is resistant to electromigration and free of micro-voids, enabling reliable scaling to higher device densities
Solution Approach 2:
The patent creates a composite structure with Ru and Cu layers, where the optimized Ru film provides a foundation for large-grain Cu growth, resulting in a composite interconnect structure with superior electrical and mechanical properties for scaled devices
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 method prevents micro-voids and enhances Cu grain growth, reducing electrical resistivity and increasing the reliability of Cu-filled recessed features in integrated circuits.
Implementation Method 1
depositing a continuous Ru metal film in the recessed feature by thermal chemical vapor deposition (TCVD) using a process gas containing a Ru3(CO)12 precursor
Implementation Method 2
thermal chemical vapor deposition (TCVD) using a process gas containing a Ru3(CO)12 precursor
Implementation Method 3
annealing the continuous Cu metal layer in a non-oxidizing gas
Data Source
AI summary
Methods are provided for multi-step Cu metal plating on a continuous Ru metal film in recessed features found in advanced integrated circuits. The use of a continuous Ru metal film prevents formation of undesirable micro-voids during Cu metal filling of high-aspect-ratio recessed features, such as trenches and vias, and enables formation of large Cu metal grains that include a continuous Cu metal layer plated onto the continuous Ru metal film. The large Cu grains lower the electrical resistivity of the Cu filled recessed features and increase the reliability of the integrated circuit.