TiW Layer Over Copper Interconnect Stack
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Solution Overview
Problem
The high cost of gold used in compound semiconductor devices for interconnects, due to its expensive nature, necessitates a more affordable alternative with similar electrical and thermal properties, while copper, though desirable, requires barrier layers to prevent diffusion and oxidation.
Innovation Solution
A metalized structure for compound semiconductor devices is proposed, featuring a titanium (Ti) layer as an adhesion layer, a barrier layer such as platinum (Pt) or palladium (Pd), a copper (Cu) layer to replace gold, and additional Ti or TiN layers to inhibit alloying and diffusion, with a gold layer for passivation, all formed by evaporation or sputtering techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold is used for interconnects in compound semiconductor devices, then electrical conductivity and chemical inertness are improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent employs a composite interconnect structure consisting of multiple layers: copper provides electrical conductivity, titanium nitride serves as a diffusion barrier, and titanium provides adhesion. This composite approach combines the advantages of different materials while mitigating their individual disadvantages, achieving gold-like performance at lower cost.
Solution Approach 2:
The patent replaces expensive gold with cheaper copper-based interconnect structures. While copper is more reactive than gold, the use of protective barrier layers (titanium nitride and titanium) enables copper to function effectively as a long-lasting interconnect material, making the 'cheap material' approach viable.
2Ease of manufacture
If copper is used to replace gold in interconnects, then manufacturing cost decreases, but copper diffusion and oxidation occur without barrier layers
Solution Approach 1:
The patent introduces titanium nitride as an intermediary barrier layer between copper and the semiconductor substrate. This intermediate layer prevents direct interaction between copper and the substrate, blocking copper diffusion while allowing the copper interconnect to function. The titanium layer serves as another intermediary providing both adhesion and additional diffusion protection.
Solution Approach 2:
The interconnect structure is designed as a composite of copper (for conductivity), titanium nitride (for diffusion barrier), and titanium (for adhesion and barrier). This composite structure enables copper to be used without suffering from its inherent diffusion and oxidation problems.
3Stability of the object's composition
If multiple barrier layers are added to prevent copper diffusion, then copper stability is improved, but device structure complexity increases
Solution Approach 1:
The titanium layer serves multiple functions simultaneously: it provides adhesion between the copper interconnect and the semiconductor substrate, acts as a diffusion barrier, and contributes to the overall structural integrity. This multi-functionality reduces the need for additional separate layers, simplifying the overall structure while maintaining stability.
Solution Approach 2:
The patent uses a composite barrier system where titanium nitride and titanium layers work together to provide comprehensive protection against copper diffusion. The synergistic combination of these materials achieves superior barrier performance compared to single-layer approaches, allowing for optimized thickness and reduced 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 configuration provides a cost-effective alternative to gold, ensuring reliable electrical conductivity and thermal performance, with the Ti and Pt layers preventing copper diffusion and oxidation, thus maintaining device integrity under high temperature operating conditions.
Implementation Method 1
a sputtered titanium tungsten (TiW) layer disposed over the copper interconnect stack structure
Implementation Method 2
all formed by evaporation or sputtering techniques
Data Source
AI summary
Disclosed are devices and methods related to metallization of semiconductors. A metalized structure can include a stack disposed over a compound semiconductor, with the stack including a barrier, a copper (Cu) layer disposed over the barrier, and a first titanium (Ti) layer disposed over the Cu layer. The metalized structure can further include a sputtered titanium tungsten (TiW) layer disposed over the first Ti layer. The barrier can include an assembly of titanium nitride (TiN) and Ti layers. The metalized structure can further include a second Ti layer disposed over the sputtered TiW layer.