Doug Hale <doughale@...>
ICs use aluminum as the interconnect between the devices in the substrate. Aluminum is a relatively soft metal.
The way ICs get denser is to shrink device geometry's and make smaller interconnects. There is a limit
as to how small the aluminum geometry's can go, partially due to metal migration. That is why it has been
in the news that IBM has developed the processes to use copper which is harder (migrates less) under
the same conditions. It can, therefore, be made smaller than aluminum which yields smaller parasitic
capacitance and higher speeds.