Copper Vs. Aluminum

Over the last few years there has been a debate on the merits of copper versus aluminum interconnects. Copper offers lower resistance and better electro-migration properties but adds complexity to the fabrication process. It is also more difficult to use low-K dielectrics with copper.

These are some of the reasons why Intel decided to implement their 1 GHz version of the Coppermine processor in 0.18 µ CMOS with aluminum interconnects: aluminum metal lines combined with SiOF low-K dielectric and decreased gate dimensions enable higher speed transistors. The architectural enhancements include a 256 kByte Advanced Transfer Cache (ATC). It offers a bandwidth of 16 GByte/s to the L2 cache, lower latency (4x improvement in L2 latency over the Pentium III processor) and higher cache associativity (8-way set associative, 1024 sets).

As Intel elaborated at the press conference, making changes to the architecture was less of a risk than switching to copper and potentially decreasing the yield for a high volume product. However, for the next shrink to 0.13 µ the company will utilize copper interconnects.

AMD did not present a paper at the ISSCC but demonstrated a system running on a 1.1 GHz Athlon. The chip was manufactured at the Fab 30 facility in Dresden, Germany, using AMD's HiP6L 0.18 µ process with copper interconnects. The system did not require any special cooling techniques. According AMD the speedy Athlon will hit the streets in the fourth quarter of this year. It is most likely that Intel will time the launch of its 1 GHz Coppermine processor accordingly. The chip is going to ship before their next processor named Willamette.

It seems that the 1 GHz barrier is not a roadblock anymore. The latest news from the Intel Developer Forum going on in Palm Springs this week report that Intel Chairman Andy Grove showed off a 1.5 GHz Willamette processor operating at room temperature. The race continues...