Group II Alloy Seed Layers for Interconnect Resistance and Integrity
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Solution Overview
Problem
The challenge in integrated circuits is to reduce the resistance and coupling capacitance of metal interconnects to mitigate RC-delay, while maintaining mechanical and chemical integrity, as copper interconnects are prone to electro-migration and existing low-K dielectric layers and air-gap technologies have limitations.
Innovation Solution
Incorporating Group II element alloys, such as copper-beryllium, as seed or barrier layers to decrease line resistance, increase mechanical integrity, and inhibit electro-migration, along with forming air-gap metal interconnect architectures to reduce capacitance and enhance chemical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper interconnects are used to reduce resistance, then electrical conductivity is improved, but electro-migration occurs compromising reliability
Solution Approach 1:
The patent applies composite materials by combining copper with Group II element alloys (such as magnesium, calcium, strontium, or barium) to create a composite interconnect structure. This composite approach allows the copper to provide low resistance while the Group II element alloy forms a protective barrier layer that prevents electro-migration, thus resolving the contradiction between electrical conductivity and reliability.
Solution Approach 2:
The Group II element alloy acts as an intermediary barrier layer between the copper interconnect and the surrounding environment. This intermediary layer blocks the migration of copper atoms while maintaining the electrical conductivity of the copper core, effectively mediating between the need for low resistance and the prevention of electro-migration.
2Loss of energy
If low-K dielectric layers are used to reduce coupling capacitance, then capacitance is decreased, but manufacturing complexity increases
Solution Approach 1:
The patent changes the dielectric constant parameter by using air gaps (K=1) instead of traditional low-K dielectric materials (K=2.5-4). This parameter change dramatically reduces coupling capacitance between interconnects while simplifying the manufacturing process, as air gaps can be formed through self-aligned processes without requiring complex deposition and patterning of low-K materials.
Solution Approach 2:
The patent extracts the dielectric material entirely from the interconnect spacing regions, replacing it with air gaps. This extraction eliminates the need to manufacture and integrate low-K dielectric layers, thereby reducing coupling capacitance while simultaneously decreasing manufacturing complexity by removing a complex material deposition and patterning step.
3Loss of energy
If air-gap technology is used to reduce coupling capacitance, then capacitance is decreased, but mechanical integrity is compromised
Solution Approach 1:
The patent applies local quality by providing different structural characteristics in different regions: air gaps are used in the horizontal spacing regions between interconnects to reduce capacitance, while the Group II element alloy barrier layers are positioned locally at the interfaces and surrounding the copper interconnects to provide mechanical support and chemical protection. This localized application of different materials resolves the contradiction between capacitance reduction and mechanical integrity.
Solution Approach 2:
The patent creates a composite structure where air gaps coexist with Group II element alloy barrier layers that surround and support the copper interconnects. This composite architecture allows the air gaps to reduce capacitance while the alloy barrier layers maintain mechanical integrity, preventing the interconnects from collapsing or deforming in the absence of traditional dielectric support.
Data Source
AI summary
A plurality of metal interconnects incorporating a Group II element alloy for protecting the metal interconnects and methods to form and incorporate the Group II element alloy are described. In one embodiment, a Group II element alloy is used as a seed layer, or a portion thereof, which decreases the line resistance and increases the mechanical strength of a metal interconnect. In another embodiment, a Group II element alloy is used to form a barrier layer, which, in addition to decreasing the line resistance and increasing the mechanical integrity, also increases the chemical integrity of a metal interconnect.