Semiconductor Interconnect Oxygen Intrusion Mitigation
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Solution Overview
Problem
Copper-based semiconductor interconnect structures face issues with oxygen intrusion, leading to oxidation of diffusion barriers, electromigration voids, and extrusions/hillocks, which reduce performance and reliability due to inadequate impurity segregation and copper diffusion.
Innovation Solution
A method involving a sacrificial oxidation layer, a barrier metal layer, and a seed layer with impurities like manganese, followed by an electroplated copper layer, where a capping layer is formed to minimize oxygen intrusion and enhance impurity segregation, suppressing copper diffusion and electromigration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If copper is used for interconnects to achieve low resistivity and high current carrying capacity, then signal transmission speed is improved, but electromigration occurs causing void formation and extrusion/hillock formation
Solution Approach 1:
A sacrificial oxidation layer is formed on the dielectric layer before depositing the barrier metal layer and copper interconnect. This oxidation layer is strategically placed to consume oxygen that would otherwise diffuse into the copper, preventing oxidation of the barrier interface and subsequent electromigration void formation. The preliminary action of creating this protective layer eliminates the harmful oxygen intrusion before it can affect the copper interconnect structure.
2Quantity of substance
If oxygen is present in the interconnect structure, then oxidation of diffusion barrier material occurs forming an oxidized barrier interface, but this oxidized interface serves as an electromigration void nucleation site accelerating void growth
Solution Approach 1:
The sacrificial oxidation layer converts the harmful presence of oxygen into a beneficial protective function. By intentionally allowing oxygen to react with the sacrificial layer (which is designed to be oxidizable), the oxygen is consumed and trapped in the oxidation layer, preventing it from reaching and oxidizing the barrier metal interface. This transforms oxygen from a harmful element causing electromigration into a controlled component that protects the copper interconnect.
3Quantity of substance
If impurities like manganese and aluminum are present in the seed layer, then they can segregate in regions susceptible to copper diffusion to suppress copper diffusion, but oxygen consumes these impurities preventing their segregation
Solution Approach 1:
The sacrificial oxidation layer is formed before depositing the seed layer containing impurities like manganese and aluminum. This preliminary oxidation layer acts as an oxygen barrier, preventing oxygen from consuming the impurities in the seed layer. As a result, the impurities remain available to segregate at the copper-dielectric interface, forming a protective barrier that suppresses copper diffusion and prevents electromigration void formation.
4Reliability
If a multi-layer structure with sacrificial oxidation layer, barrier metal layer, seed layer, and electroplated copper layer is formed, then oxygen intrusion is minimized and impurity segregation is enhanced, but the device complexity increases
Solution Approach 1:
The interconnect structure is segmented into distinct functional layers: a sacrificial oxidation layer for oxygen consumption, a barrier metal layer for copper diffusion prevention, a seed layer with controlled impurities for interface protection, and an electroplated copper layer for current conduction. Each layer performs a specific function, and the segmentation allows independent optimization of each layer's properties and thickness to achieve reliable copper interconnects while managing structural complexity.
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 reduces void and extrusion/hillock formation, improving the reliability and performance of semiconductor interconnects by minimizing oxygen intrusion and enhancing impurity segregation, thus extending the useful life of integrated circuit products.
Implementation Method 1
oxygen intrusion into the seed layer and electroplated copper layer of the interconnect structure causes oxidation of diffusion barrier material
Implementation Method 2
An electroplated copper layer is disposed on the seed layer
Implementation Method 3
The segregating of impurities in certain regions of the interconnect structure that are susceptible to copper diffusion is important for suppressing copper diffusion
Data Source
AI summary
An interconnect structure and method for fabricating the interconnect structure having enhanced performance and reliability, by minimizing oxygen intrusion into a seed layer and an electroplated copper layer of the interconnect structure, are disclosed. At least one opening in a dielectric layer is formed. A sacrificial oxidation layer disposed on the dielectric layer is formed. The sacrificial oxidation layer minimizes oxygen intrusion into the seed layer and the electroplated copper layer of the interconnect structure. A barrier metal layer disposed on the sacrificial oxidation layer is formed. A seed layer disposed on the barrier metal layer is formed. An electroplated copper layer disposed on the seed layer is formed. A planarized surface is formed, wherein a portion of the sacrificial oxidation layer, the barrier metal layer, the seed layer, and the electroplated copper layer are removed. In addition, a capping layer disposed on the planarized surface is formed.