The Microelectronics Division was interested in the copper process, but it was suspicious of the use of polyamide as the insulator, because it tends to be cut and scratched by damascene polishing. In addition, research at the Almaden Research Center had shown that polyamide was not as effective an insulator as originally thought.
The IBM team decided not to try changing both the metal and the insulator together. In late 1993, it was suggested that it would be better to deposit copper on the familiar silicon dioxide insulator, using the dual-damascene process. This would save money for CMOS manufacturing and also improve reliability and yield.
When the team put this process to the test the first few wafers made were of higher quality than those with polyamide. Even better news followed when the group processed larger wafers in the test facility at the ASTC - By that time, the performance of CMOS technology had improved to the point at which aluminum circuitry was reaching its limit.
At the end of 1999 IBM posted this news - "IBM Corp. has developed a 0.18-micron manufacturing process that combines silicon germanium transistors with copper interconnects to create devices that have exhibited speeds as high as 90 GHz.", and when looking at SIA's Roadmap for the next ten years, we really have something to look forward to:
Fig. 3 SIA Roadmap for the next ten years.