Forum › Category: Layout › Why is Copper replacing Aluminium in modern VLSI Fabrication Processes?
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Avatarsemiconductor asked 2 months ago
I think it's important to understand that each metallization layer in chip design has specific requirements to ensure efficient routing. For every routing layer, there are two corresponding layers, such as Contact + Metal1 or Via[n] + Metal[n+1]. You need these pairs to handle the complex routing in modern circuits. For the materials, aluminium has been widely used because it meets many necessary criteria, like good conductivity and easy deposition. However, I see why chip manufacturers are moving to copper. It has a lower specific resistance and can handle higher current densities than aluminium, which is vital for smaller, more compact chip designs.
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AvatarCircuitDesigner answered 2 months ago
When we talk about the shift from aluminum to copper for interconnects, it's mostly about performance and practicality. We see aluminum being good for conductivity and stability, but when features shrink, the parasitic resistance becomes an issue. This is where copper comes in. It not only has lower resistance but also reduces electromigration. But you also have to be aware of the challenges. Copper tends to contaminate and corrode, so it requires protective coatings, which complicates the fabrication process. You need to balance the benefits and difficulties when choosing materials for these layers in your layout design.
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AvatarDigitalWorld answered 2 months ago
You have to consider that in chip fabrication, material choice isn’t just about conductivity. We, as designers, have to think about current-carrying capacity, corrosion resistance, and even mechanical stability over time. Aluminum was great for many years, but as chip designs have become more compact, it’s not as effective because of increased parasitic resistance. So, moving to copper makes sense despite its issues with contamination and the need for special structuring techniques. Copper’s benefits, like faster signal propagation due to reduced parasitic effects, are significant enough that the extra fabrication challenges are worth it.