Selective W-CVD Capping on Cu Interconnections
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Solution Overview
Problem
Conventional selective CVD methods for forming a W-capping film on Cu electrical interconnections suffer from selectivity breakage due to pre-treatment methods like H2-annealing or H2-plasma treatments, which cause the W-film to deposit on both Cu-electrical interconnections and electrical insulating films, leading to reduced reliability and the need for etch back steps.
Innovation Solution
Inactivating the surface of the electrical insulating film through nitrogenation or alkylation using gases containing N, H, and Si atoms, such as NH3, N2, H2, and silanols, to prevent raw gas adsorption and decomposition, ensuring selective W-capping film formation only on Cu-containing electrical interconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If H2-annealing treatment or H2-plasma treatment is used as pre-treatment, then the Cu surface is cleaned and activated for W-film formation, but the electrical insulating film surface is also activated causing W-film to deposit on it, breaking selectivity
Solution Approach 1:
The patent applies preliminary action by performing a specific pre-treatment sequence: first treating with H2 plasma to clean and activate the Cu surface, then immediately treating with NF3 plasma to passivate the electrical insulating film surface by forming a fluorinated layer. This preliminary passivation prevents W-film deposition on the insulating film during subsequent W-CVD processing, thereby maintaining selectivity while ensuring proper Cu surface activation.
2Reliability
If conventional selective CVD process with pre-treatment is used, then W-capping film can be formed on Cu electrical interconnection, but etch back step is required to remove W-film from insulating film, reducing process efficiency
Solution Approach 1:
The patent eliminates the need for etch back by performing preliminary passivation with NF3 plasma treatment immediately after H2 plasma treatment. The NF3 treatment forms a protective fluorinated layer on the electrical insulating film surface before W-CVD begins, preventing W-film deposition entirely. This approach maintains the reliability of capping film formation on Cu interconnections while improving productivity by removing the subsequent etch back step.
3Manufacturing precision
If H atoms terminate the electrical insulating film surface through pre-treatment, then Cu surface is activated for W-growth, but activated sites are formed on insulating film allowing WF6 to react and etch the film, breaking selectivity
Solution Approach 1:
The patent introduces NF3 plasma treatment as an intermediary step between H2 plasma treatment and W-CVD. The NF3 treatment acts as a mediator that converts the harmful H-terminated surface on the electrical insulating film into a stable fluorinated surface. This intermediary treatment prevents direct reaction between WF6 and the insulating film, eliminating HF generation and etching, thereby restoring selectivity to the W-film growth process.
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 maintains selectivity in the W-CVD method, allowing for efficient formation of a W-capping film on Cu-electrical interconnections without depositing on insulating films, thereby enhancing the reliability of multi-layered Cu-electrical interconnections.
Implementation Method 1
Inactivating the surface of the electrical insulating film through nitrogenation or alkylation using gases containing N, H, and Si atoms, such as NH3, N2, H2, and silanols
Implementation Method 2
Inactivating the surface of the electrical insulating film through nitrogenation or alkylation using gases containing N, H, and Si atoms, such as NH3, N2, H2, and silanols
Implementation Method 3
prevent raw gas adsorption and decomposition
Implementation Method 4
introducing a raw gas into the vacuum chamber to thus selectively form a W-capping film on the surface of the Cu-containing electrical interconnection film
Data Source
AI summary
A substrate provided thereon with an electrical insulating film which carries holes or the like filled with a Cu-containing electrical interconnection film is subjected to a pre-treatment in which the surface of the electrical insulating film and that of the Cu-containing electrical interconnection film are treated at a temperature of not more than 300° C. using, in a predetermined state, a gas of a compound containing an atom selected from the group consisting of N, H and Si atoms within the chemical formula thereof, before selectively forming a W-capping film on the electrical interconnection film. After the completion of the pre-treatment, a W-capping film is selectively formed on the electrical interconnection film and then an upper Cu electrical interconnection is further formed.