Cu Interconnection Openings Cleaned by Superheated Steam
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Solution Overview
Problem
In semiconductor device fabrication, the oxidation of barrier metal films due to water and fluorine residues in the interlayer insulation film leads to issues like dilatation, cracking, and increased dielectric constant, affecting the adhesion and electric properties of Cu interconnection structures.
Innovation Solution
A method using superheated steam to remove CFx molecules and terminating fluorine from the sidewall and bottom surfaces of openings in the interlayer insulation film, preventing oxidation of refractory metal barrier films and maintaining the low dielectric constant of low-K dielectric films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dry etching process using fluorine-containing etching gas is used to form openings, then the openings can be precisely formed in the interlayer insulation film, but water and fluorine residues remain on the sidewall and bottom surfaces, causing oxidation of barrier metal films
Solution Approach 1:
The patent applies a preliminary cleaning action using superheated steam exposure before depositing the barrier metal film. This removes water and fluorine residues from the opening surfaces in advance, preventing oxidation of the barrier metal film that would otherwise occur during subsequent processing steps.
Solution Approach 2:
The patent changes the physical parameters of the cleaning medium by using superheated steam instead of conventional cleaning methods. The superheated steam effectively removes residues without causing oxidation, and the subsequent introduction of a reducing atmosphere further prevents oxidation of the barrier metal film.
2Device complexity
If barrier metal films are deposited without removing fluorine residues, then the deposition process can be simplified, but the barrier metal films undergo oxidation leading to dilatation and cracking
Solution Approach 1:
The patent performs preliminary removal of fluorine residues using superheated steam and introduces a reducing atmosphere before barrier metal film deposition. This prevents oxidation during deposition, maintaining film integrity without requiring complex in-situ cleaning integrated into the deposition chamber.
Solution Approach 2:
The patent introduces a reducing atmosphere as an intermediary environment between the dry etching process and barrier metal film deposition. This reducing atmosphere acts as a protective medium that prevents oxidation of the barrier metal film while allowing for simple deposition processes.
3Device complexity
If Cu atoms directly contact the interlayer insulation film, then the structure can be simplified, but Cu atoms invade into the interlayer insulation film by diffusion causing short circuits
Solution Approach 1:
The patent uses a barrier metal film as an intermediary layer between the Cu interconnection pattern and the interlayer insulation film. This barrier metal film prevents Cu atom diffusion into the insulation film, avoiding short circuits while maintaining structural simplicity.
Solution Approach 2:
The patent extracts the harmful diffusion barrier function from the interlayer insulation film itself and places it in a dedicated barrier metal film layer. This specialized barrier layer is specifically designed to prevent Cu atom diffusion, improving reliability without complicating the overall structure.
4Reliability
If superheated steam is used to clean the opening surfaces, then oxidation of barrier metal films is suppressed, but additional process steps are required
Solution Approach 1:
The superheated steam cleaning is performed as a preliminary step before barrier metal film deposition, ensuring surfaces are free of residues that would cause oxidation. This separate preliminary step protects the barrier metal film adhesion without requiring integration into the deposition process itself.
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 effectively suppresses oxidation of barrier metal films, enhances adhesion, and maintains the low dielectric constant of interlayer insulation films, resulting in improved yield and reduced contact resistance in multilayer interconnection structures.
Implementation Method 1
cleaning a bottom surface and a sidewall surface of the opening by exposing to a superheated steam
Implementation Method 2
remove CFx molecules and terminating fluorine from the sidewall and bottom surfaces of openings
Implementation Method 3
cover the bottom surface and the sidewall surface of the opening with a barrier metal film
Implementation Method 4
preventing oxidation of refractory metal barrier films
Implementation Method 5
polishing the conductor film and the barrier metal film underneath the conductor film by a chemical mechanical polishing process
Implementation Method 6
chemical mechanical polishing process
Data Source
AI summary
A method of forming an interconnection structure includes forming an opening in an insulation film by a dry etching process that uses an etching gas containing fluorine; cleaning a bottom surface and a sidewall surface of the opening by exposing to a superheated steam; covering the bottom surface and the sidewall surface of the opening with a barrier metal film; depositing a conductor film on the insulation film via the barrier metal film to fill the opening with the conductor film; forming an interconnection pattern by the conductor film in the opening by polishing the conductor film and the barrier metal film underneath the conductor film by a chemical mechanical polishing process until a surface of the insulation film is exposed.