Return of Aluminum Interconnects
The rising copper prices are leading some companies to re-examine aluminum, particularly for price-sensitive commodity products at older process nodes.
Copper interconnects, which completely changed design at 130nm—along with a shift to 300mm wafers and low-k dielectric insulation—are getting a second look. In fact, they’re actually being used in some chips at 110 nm and larger.
The reason is the cost, say industry sources. When copper interconnects were first under consideration in the late 1990s, copper sold for less than $1 a pound. The price peaked at $4 a pound this summer, before retreating to the current $3.25. But no matter how you cut it, that’s a significant price hike.
Aluminum isn’t free of significant price increases, either, although it’s not rising as quickly. A story by TimesOnline said that aluminum prices are expected to increase by about a third in the next couple years, in large part because the cost of running aluminum smelting plants is skyrocketing. That would increase the price to about $4,000 a ton, compared with $6,000 to $8,000 a ton for copper over the past few months.
While it’s true that chips require very small quantities of either copper or aluminum, in volume the numbers can mean the difference between a vendor winning a contract or losing it to a lower-priced competitor.
Copper will continue to be used in the most advanced chips, and road maps from the Common Platform, Intel and TSMC all show copper interconnects in future generations of chips. But in commodity applications, particularly those running at older process nodes, every penny counts.
“Some applications do not need to go to advanced geometries,” said an industry source. “These are particularly cost-sensitive applications. You will see aluminum interconnects at 110 nm and 130 nm become qualified for automotive applications in the near future.”
–Ed Sperling
Tags: Architectural, ASIC