Air Gap Interconnect Structure Using Permeable Membrane Etching
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Solution Overview
Problem
Current methods for creating air cavities in interconnect structures for integrated circuits face challenges such as high manufacturing costs, material development complexities, and potential damage to metallic lines due to chemical etching solutions, particularly with sacrificial materials like silicon oxide and thermally degradable materials, which are not reliably integrated in the medium term.
Innovation Solution
A method involving the deposition of a sacrificial material, followed by a permeable membrane layer that allows etchant diffusion to form air cavities before conductor deposition, using materials like SiO2 and SiC, with a membrane consolidation layer to maintain structural integrity and avoid collapse, and subsequent etching and polishing steps to achieve air-separated conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical etching solutions are used to remove sacrificial material, then air cavities are formed, but metallic lines are damaged through corrosion and dissolution
Solution Approach 1:
A membrane layer is introduced as an intermediary between the chemical etching solution and the metallic lines. This membrane allows the etchant to reach and remove the sacrificial material to form air cavities, while simultaneously protecting the metallic lines from direct contact with the corrosive solution, thus preventing corrosion and dissolution
Solution Approach 2:
The structure is segmented into distinct functional layers: the sacrificial material layer for cavity formation, the membrane layer for selective protection, and the metallic line layer. This segmentation allows the etching process to be localized to specific regions (where sacrificial material exists) while protecting other regions (metallic lines) from harmful chemical effects
2Manufacturing precision
If new materials like porous membranes or thermally degradable materials are developed for sacrificial layers, then air cavity formation is enabled, but manufacturing complexity and development time increase
Solution Approach 1:
The invention uses silicon oxide as a sacrificial material that can be easily deposited using standard PECVD processes and completely removed by hydrofluoric acid etching. This disposable sacrificial layer approach avoids the need for complex reusable materials, simplifying the overall manufacturing process while enabling reliable air cavity formation
Solution Approach 2:
The membrane layer serves multiple functions simultaneously: it acts as a protective barrier during etching, provides structural support to prevent collapse, and allows selective diffusion of etchant molecules. This multi-functionality reduces the need for additional specialized materials and process steps
3Manufacturing precision
If sacrificial material is removed by thermal degradation, then air cavities are formed, but complete decomposition with residue evacuation is difficult to achieve
Solution Approach 1:
The invention replaces thermal degradation with chemical etching for sacrificial material removal. Hydrofluoric acid solution is used to chemically dissolve silicon oxide sacrificial material, providing complete and clean removal without leaving carbonaceous residues that would contaminate the air cavities or require additional evacuation steps
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 method enables reliable integration of air cavities with reduced material development needs, maintains conductor integrity, and minimizes the impact of etching solutions on the structure, ensuring stable electrical performance and compatibility with existing manufacturing processes.
Implementation Method 1
depositing a membrane layer of material permeable to an etchant for decomposing the sacrificial material, decomposing the sacrificial material by means of the etchant
Implementation Method 2
the etching of the sacrificial material to retain only the portions where the air cavities must be formed
Data Source
Figure 1A~2F
Figure 3~7
Figure 8A~8F
AI summary
The invention relates to a method for manufacturing a Damascus-type electrical interconnection structure for an integrated circuit, comprising at least one interconnection level, consisting of electrical conductors arranged on a substrate and separated from each other by air cavities, a layer of electrically insulating material covering the interconnection level, the method comprising the steps of: - depositing a layer of sacrificial material on the substrate, - etching the layer of sacrificial material according to a pattern corresponding to the electrical conductors, - depositing, on the etched layer of the sacrificial material layer, a membrane layer of material permeable to an etching agent enabling the decomposition of the sacrificial material, - decomposing the sacrificial material by means of the etching agent, thereby forming air cavities in place of the decomposed sacrificial material.- to form the electrical conductors in the etching pattern to obtain electrical conductors separated by air cavities, - to deposit a layer of electrically insulating material to cover the resulting interconnection layer.