Copper Metallization Filling High-Aspect-Ratio Openings Without Voids
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Solution Overview
Problem
Existing methods for forming metal structures in integrated circuits face challenges in filling high aspect ratio openings without voids and require diffusion barrier layers, especially at reduced feature sizes.
Innovation Solution
A method involving gas-induced metal migration through oxidation and reduction reactions forms a second metal structure without a diffusion barrier layer, utilizing gases like hydrogen and oxygen to fill openings efficiently and form a metal structure with controlled oxygen concentration gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional metal deposition methods are used to fill high aspect ratio openings, then the openings can be filled with metal structures, but voids form within the filled structures
Solution Approach 1:
The patent replaces conventional mechanical deposition methods (PVD, CVD) with a chemical migration mechanism. Metal atoms migrate through the dielectric layer via diffusion driven by oxygen concentration gradients, naturally filling high aspect ratio openings without voids formed by line-of-sight deposition limitations
Solution Approach 2:
The patent changes the oxygen concentration parameter by introducing oxygen plasma or oxygen-containing gases. This creates oxygen concentration gradients that drive metal atom migration, transforming the filling mechanism from mechanical deposition to chemically-driven diffusion that eliminates void formation
2Reliability
If diffusion barrier layers are added to prevent metal diffusion, then metal contamination of dielectric layers is prevented, but the process complexity and material usage increase
Solution Approach 1:
The patent extracts and removes the diffusion barrier layer from the conventional metal interconnect structure. By controlling the migration process through oxygen concentration gradients and selective stopping layers, the system achieves metal diffusion control without requiring additional barrier layer materials
Solution Approach 2:
The migrating metal atoms self-limit their migration when encountering regions with sufficient oxygen concentration (such as doped semiconductor regions or oxide layers). This self-stopping mechanism eliminates the need for external diffusion barrier layers while preventing metal contamination
3Productivity
If metal layer thickness is reduced to improve integration, then higher density interconnects are achieved, but control over oxygen concentration and material spread becomes more difficult
Solution Approach 1:
The patent creates local variations in oxygen concentration throughout the structure. Oxygen-rich regions (doped semiconductors, oxides) act as stopping points for metal migration, while oxygen-poor regions allow controlled metal flow. This local quality control enables precise thickness control even in reduced-thickness layers
Solution Approach 2:
The migration process incorporates inherent feedback through oxygen concentration sensing. Metal atoms naturally stop migrating when they encounter regions with sufficient oxygen, providing self-regulation of layer thickness and preventing uncontrolled material spread in thin-layer structures
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 achieves void-free metal structures with controlled oxygen concentration, allowing for thinner metal layers and reduced material spread, enhancing integration and performance in integrated circuits.
Implementation Method 1
A gas is provided that induces metal material from the metal structure to migrate into the opening. The gas may cause oxidation and reduction of the metal material
Implementation Method 2
The gas may cause oxidation and reduction of the metal material
Implementation Method 3
The interaction causes metal material from the first metal structure to migrate into the opening where it forms the second metal structure
Data Source
AI summary
A second metal structure such as a metal plug is formed over a first metal structure, such as a metal line, by causing metal material from the first metal structure to migrate into an opening in a dielectric layer over the first metal structure. The metal material, which may be copper, is of a type that undergoes a reduction in density as it oxidizes. Migration is induced using gases that alternately oxidize and reduce the metal material. Over many cycles, the metal material migrates into the opening. In some embodiments, the migrated metal material partially fills the opening. In some embodiments, the migrated metal material completely fills the opening.