Bimetallization Interconnects for Void-Free Dual Damascene Vias
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Solution Overview
Problem
Advanced dual damascene interconnect structures face issues with copper voids and small grain size, leading to poor electromigration performance, necessitating the development of void-free vias and large-grained copper lines using alternative metals.
Innovation Solution
The semiconductor structure incorporates a bimetallization interconnect structure with a first electrically conductive metal or alloy having a specific bulk resistivity surrounded by a second metal or alloy with lower resistivity and a grain size greater than 10 nm, achieved through a method involving multiple layers and reflow anneal processes to enhance conductivity and grain size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper or copper alloy is used as the material of electrically conductive metal vias and lines, then electrical conductivity is improved, but copper voids and small grain size lead to poor electromigration performance
Solution Approach 1:
The patent employs a composite metallization structure consisting of a first electrically conductive metal or alloy (such as copper) and a second electrically conductive metal or alloy (such as copper alloy). This composite structure combines the high conductivity of pure copper with the enhanced mechanical properties and larger grain size of copper alloys, thereby improving electromigration performance while maintaining electrical conductivity. The multi-material approach allows each material to contribute its advantageous properties to the overall interconnect structure.
Solution Approach 2:
The patent applies different material compositions to different regions of the interconnect structure. Specifically, the via region may use one composition while the line region uses another, or the structure transitions from a first electrically conductive metal/alloy to a second electrically conductive metal/alloy along the interconnect path. This local differentiation allows optimization of each region for its specific function: via regions for electrical connection and line regions for signal transmission, thereby achieving void-free vias and large-grained copper lines with improved electromigration performance.
2Adaptability or versatility
If advanced dual damascene interconnect structures are used, then routing capability is improved, but copper voids form in the via and line portions
Solution Approach 1:
The patent modifies the material parameters of the interconnect structure by transitioning from a single copper material to a combination of first and second electrically conductive metals or alloys. This parameter change in material composition and structure prevents copper void formation by utilizing the different physical and chemical properties of the alloy materials, which have enhanced fillability and reduced void formation during the electroplating process while maintaining the advanced routing capabilities of dual damascene structures.
3Productivity
If copper grain size is reduced to less than 5 nm, then interconnect density is improved, but electromigration performance deteriorates
Solution Approach 1:
The patent creates a composite interconnect structure where a first electrically conductive metal or alloy (providing high conductivity) is combined with a second electrically conductive metal or alloy (providing larger grain size greater than 10 nm). This composite approach allows the structure to achieve both high interconnect density through the fine-scale first material and improved electromigration performance through the larger-grained second material, effectively resolving the contradiction between density and reliability.
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 vias and large-grained copper lines, improving electromigration performance and addressing the limitations of conventional dual damascene interconnect structures.
Implementation Method 1
a second electrically conductive structure composed of a second electrically conductive metal or metal alloy material having a second bulk resistivity that is less than the first bulk resistivity and a grain size greater than 10 nm
Implementation Method 2
a first electrically conductive structure composed of a first electrically conductive metal or metal alloy material having a first bulk resistivity surrounding a second electrically conductive structure
Data Source
AI summary
A structure is provided that includes a lower interconnect level that includes a first interconnect dielectric material layer having an opening that contains a first bimetallization interconnect structure. An upper interconnect level is located above the lower interconnect level. The upper interconnect level includes a second interconnect dielectric material layer having a combined via/line opening, wherein the line portion of the combined via/line opening contains a second bimetallization interconnect structure. In accordance with the present application, the first and second bimetallization interconnect structures comprises a first electrically conductive structure composed of a first electrically conductive metal or metal alloy material having a first bulk resistivity surrounding a second electrically conductive structure composed of a second electrically conductive metal or metal alloy material having a second bulk resistivity that is less than the first bulk resistivity and a grain size greater than 10 nm.