Barrier-Metal-Free Interconnect Structure for Low-Resistance Narrow Trenches
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Solution Overview
Problem
The use of barrier metals in copper interconnects increases electrical resistivity due to their higher resistivity compared to copper, making it difficult to achieve low-resistance fine interconnects, especially as interconnect widths narrow.
Innovation Solution
A method of manufacturing a barrier-metal-free metal interconnect structure by filling interconnect trenches with an intermetallic compound, followed by planarization and height adjustment processes using polishing liquids with specific removal-rate selectivities to ensure the intermetallic compound fills the trenches without excess material, thereby eliminating the need for barrier metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier metal layer is formed on the insulating layer to prevent copper diffusion, then the diffusion prevention is improved, but the electrical resistivity increases due to the higher resistivity of barrier metal compared to copper
Solution Approach 1:
The patent removes the barrier metal layer from the interconnect structure entirely, replacing it with an intermetallic compound layer that provides both diffusion prevention and low electrical resistivity. This extraction of the problematic barrier metal component resolves the contradiction by eliminating the source of high resistivity while maintaining the essential function of preventing copper diffusion into the insulating layer.
Solution Approach 2:
The patent employs an intermetallic compound (such as CuAl2 or NiAl) that combines the properties of different metals to achieve both diffusion barrier functionality and low electrical resistivity. This composite material approach allows the single layer to fulfill both requirements simultaneously, resolving the contradiction between diffusion prevention and electrical resistivity control.
2Length of moving object
If the interconnect width is reduced to achieve finer interconnects, then the integration density is improved, but the proportion of barrier metal in the interconnect increases, leading to higher resistance
Solution Approach 1:
By removing the barrier metal layer entirely and replacing it with an intermetallic compound layer, the patent eliminates the source of high resistance that becomes problematic in narrow interconnects. This allows fine interconnects to be formed without the resistance penalty that would otherwise result from the increased proportion of barrier metal.
Solution Approach 2:
The patent changes the material parameter of the barrier layer from conventional barrier metals (with high resistivity) to intermetallic compounds (with low resistivity comparable to copper). This parameter change in material composition allows narrow interconnects to maintain low resistance despite the increased relative thickness of the barrier layer.
3Device complexity
If copper is deposited directly onto the insulating layer, then the manufacturing process is simplified, but copper diffusion into the insulating layer occurs
Solution Approach 1:
The patent removes the barrier metal layer but maintains a simplified manufacturing process by directly depositing the intermetallic compound layer onto the insulating layer. This single-layer approach is actually simpler than the conventional multi-layer approach (barrier metal + copper), while simultaneously providing effective copper diffusion control through the intermetallic compound's inherent properties.
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 allows for the realization of low-resistance interconnects by filling narrow trenches with intermetallic compounds, reducing electrical resistivity and maintaining low resistance even in narrow interconnects.
Implementation Method 1
filling at least a first interconnect trench with an intermetallic compound by depositing the intermetallic compound on an insulating layer
Implementation Method 2
performing a planarization process of polishing the intermetallic compound until the insulating layer is exposed; and then performing a height adjustment process of polishing the intermetallic compound and the insulating layer
Data Source
AI summary
The present invention relates to a metal interconnect structure containing no barrier metal and a method of manufacturing the metal interconnect structure. The method includes: filling at least a first interconnect trench with an intermetallic compound by depositing the intermetallic compound on an insulating layer having the first interconnect trench and a second interconnect trench formed in the insulating layer, the second interconnect trench being wider than the first interconnect trench; performing a planarization process of polishing the intermetallic compound until the insulating layer is exposed; and then performing a height adjustment process of polishing the intermetallic compound and the insulating layer until a height of the intermetallic compound in the first interconnect trench reaches a predetermined height.