Void-Free High Aspect Ratio Metal Alloy Interconnects
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Solution Overview
Problem
Conventional metal deposition techniques fail to fill high aspect ratio openings in integrated circuits without forming voids or seams, especially as technology nodes approach the sub-10 nm range, due to limitations in conformal deposition and physical transport of metal materials.
Innovation Solution
The use of a solvent-based etchant, comprising citric acid, peroxide, and a secondary alcohol like 1,2-propanediol, which selectively and slowly recesses metal alloys in high aspect ratio structures, preventing void formation and achieving uniform metal fill with reduced surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal deposition techniques are used to fill high aspect ratio openings, then the deposition process can be performed with existing equipment, but voids or seams form in the metal fill due to limitations in conformal deposition and physical transport
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a solvent-based etchant composition with specific ratios of citric acid (0.1-5 wt%), peroxide (0.01-1 wt%), and secondary alcohol (70-95 wt%). This chemical parameter change enables selective removal of voids while preserving the metal alloy interconnect structure, achieving void-free filling in high aspect ratio openings
Solution Approach 2:
The patent employs a composite etchant system combining multiple chemical agents (citric acid, peroxide, and secondary alcohol) that work synergistically. The citric acid provides chelating action, peroxide provides oxidizing capability, and secondary alcohol provides solvent properties and controls etch rate, together enabling selective void removal without damaging the metal interconnects
2Ease of manufacture
If conventional wet etchants are used to recess metal fill, then the etching process is simple, but the metal fill surface becomes rough and non-uniform
Solution Approach 1:
The patent changes the physical and chemical parameters of the etchant by replacing conventional aqueous-based wet etchants with a solvent-based system where secondary alcohol constitutes 70-95 wt% of the composition. This parameter change reduces surface roughness to less than 1.25 RMS per nm while maintaining etching capability, achieving both process simplicity and surface quality
3Area of moving object
If feature size is scaled down to sub-10 nm range, then device density increases, but variability in fabrication processes limits further extension
Solution Approach 1:
The patent applies local quality by enabling precise control of the etching process at the nanoscale level. The solvent-based etchant provides localized and uniform etching action throughout the high aspect ratio openings, ensuring consistent results across sub-10 nm features and reducing fabrication variability
Solution Approach 2:
The patent replaces conventional mechanical/conformal deposition methods with a chemical etching approach. Instead of relying on physical transport limitations of metal atoms during deposition, the solution uses chemical dissolution of voids through the solvent-based etchant, enabling better control at sub-10 nm dimensions
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 results in void-free high aspect ratio metal alloy interconnects with improved surface smoothness and within-wafer uniformity, enabling reliable fabrication of advanced integrated circuit structures without voids or seams, even in narrow features.
Implementation Method 1
The use of a solvent-based etchant, comprising citric acid, peroxide, and a secondary alcohol like 1,2-propanediol, which selectively and slowly recesses metal alloys in high aspect ratio structures
Data Source
AI summary
An integrated circuit structure comprises a dielectric layer on a substrate. An open structure is in the dielectric layer, and a void-free metal-alloy interconnect is formed in the open structure, wherein the void-free metal-alloy interconnect comprise a metal-alloy comprising a combination of two or more metallic elements excluding any mixing effects of a seed layer or liner deposited in the open structure prior to a metal fill material, and excluding effects of any doping material on the metal fill material.