|The Damascene technique continued; Dual Damascene
By: Sverre Sjøthun, March 23, 2001 Print this article
The dual-damascene process starts out with a deposited layer of oxide, which is etched twice to form the overlapping pattern of wires and vias before the metal is applied and polished. That eliminates one metal deposition step and one polishing step from the process of creating circuitry. Going to dual-damascene with copper has significant cost benefits, and reduces the number of process steps needed to form the structure.
Applying the technology to copper required a further stage: a way of polishing copper at an acceptable rate while controlling corrosion, erosion and other defects in the patterns. IBM researchers Frank Kaufman, Vlasta Brusic and Naftali Lustig pioneered a chemical-mechanical process that proved critical to IBM's success with copper technology.
Another challenge remained: overcoming copper's tendency to diffuse in silicon. In 1984 Dale Pearson, Hu and others at IBM set out to devise a substance that would act as a diffusion barrier, preventing atoms from migrating out of a copper wire into surrounding chip material. "We worked on several materials, but one particularly stable metal emerged as a very good candidate," says Hu. By the late 1980s, the team had adapted the damascene process to deposit that diffusion barrier in silicon wafers along with copper.
Paving the road for a new generation of processors
The Damascene technique
The Damascene technique continued; Dual Damascene
What does the future hold?