Dual Damascene Interconnect Void-Free Copper Refill
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Solution Overview
Problem
Conventional copper metallization processes for semiconductor back-end-of-line interconnects, such as trench and via structures, often result in voids due to trapped additives during wet electroplating or incomplete filling during physical vapor deposition, leading to reliability issues with connections.
Innovation Solution
A unified copper metallization process involving the formation of a dual damascene interconnect structure, where a liner is deposited along the sidewalls and bottom of a trench after removing excess conductive material, followed by a copper reflow process to fill the trench void-free, ensuring better connectivity and eliminating defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet electroplating is used to deposit copper in the trench, then the copper filling speed is improved, but voids are formed due to trapped additives
Solution Approach 1:
The patent segments the copper deposition process into two distinct stages: first using electroplating for rapid initial filling, then using electroless plating to complete the fill and eliminate voids. This segmentation allows each method to perform its optimal function without the drawbacks of using either method alone.
Solution Approach 2:
The patent changes the deposition parameters by switching from electroplating (high speed, additive-trapping) to electroless plating (slower, uniform deposition without additives). This parameter change resolves the contradiction by using the appropriate deposition mode for each stage of the filling process.
2Reliability
If physical vapor deposition is used to fill the trench, then void formation is reduced, but filling completeness is insufficient
Solution Approach 1:
The patent segments the deposition approach by combining physical vapor deposition (PVD) with electroless plating. PVD provides the initial void-free foundation, while electroless plating completes the filling efficiently. This segmentation captures the advantages of both methods while mitigating their individual limitations.
Solution Approach 2:
The patent introduces electroless plating as an intermediary process between PVD and electroplating. This intermediary step ensures complete filling by providing uniform copper deposition that reaches all trench regions, bridging the gap between the partial filling of PVD and the void-causing electroplating.
3Reliability
If a full liner is deposited along the bottom and sidewalls of the trench, then barrier protection is improved, but copper filling difficulty increases
Solution Approach 1:
The patent applies local quality by depositing the liner selectively on the sidewalls rather than uniformly across the entire trench bottom and sidewalls. This localized liner application provides necessary barrier protection where needed while maintaining copper filling pathways, resolving the contradiction between protection and fillability.
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 process effectively prevents voids in copper layers, enhancing the reliability and quality of interconnects by ensuring complete filling and reducing defects, thereby improving the overall performance of semiconductor devices.
Implementation Method 1
depositing a liner along a bottom and a sidewall of the trench
Implementation Method 2
copper reflow process to fill the trench void-free
Data Source
AI summary
A method including forming a dual damascene interconnect structure comprising a metal wire above a via, recessing the metal wire to form a trench, depositing a liner along a bottom and a sidewall of the trench, and forming a new metal wire in the trench. The method may also include forming a dual damascene interconnect structure comprising a metal wire above a via, recessing the metal wire to form a trench, depositing a liner along a bottom and a sidewall of the trench, removing the liner along the bottom of the trench, and forming a new metal wire in the trench.