Chip-level copper circuitry

A new dielectric material, developed by researchers at the

, could facilitate the use of copper circuitry at the chip level.

The thermally stable aromatic polymer has a low dielectric constant of 1.85, good mechanical properties and excellent adhesion.

Replacing aluminium with copper as the multilayer interconnect structure in microelectronic devices could enhance both miniaturization and performance. Copper offers much higher electrical and thermal conductivity than aluminium. Placing narrow copper lines close together, however, requires a good dielectric to reduce cross talk between wires. Unfortunately, existing dielectric insulators can't withstand the rigors of the aggressive chemical-mechanical polishing step used to produce a smooth copper surface.

"We developed an aromatic thermosetting polymer for use as an insulating material in copper chip technology," said James Economy, a professor of materials science and engineering at Illinois. "The material has a high thermal stability, low moisture pick-up and can withstand chemical-mechanical polishing."

The material that Economy and former graduate student Youngqing Huang (now at DuPont) started with had a dielectric constant of 2.7. By adding porogens - materials that leave tiny holes when they evaporate - the researchers lowered the dielectric constant to 1.85, while maintaining an acceptably high level of hardness and stiffness.