This microprocessor cross section shows empty space in between the chip’s copper wiring. Wires are usually insulated with a glasslike material, but IBM has used self-assembly techniques, which can be employed in chip-making facilities, to create air gaps that insulate the wires.
The new self-assembly approach ushers in to chip making an era of nanotechnology, says Daniel Edelstein, IBM fellow and chief scientist for the self-assembly air-gap project. Importantly, Edelstein says, IBM's process is designed to be compatible with current manufacturing facilities and materials.
IBM researchers used a new type of polymer to help them create the air gaps. The polymer is poured onto copper wires that are embedded in an insulating material. When the polymer is heated, the molecules pull away from each other to form a regular array of nanoscale holes. These holes are used as a template to etch hollow columns into the insulating material that surrounds the wires. Engineers then pump plasma, an electrically charged gas, through the holes to blast away the remaining insulating material. A quick chemical rinse leaves behind clear gaps of air on either side of the copper wires.
IBM's Edelstein says that because the new process adds manufacturing steps to the overall chip-making process, there will be a slight increase in cost. There are 10 layers of wiring in a chip, and he estimates that the cost will increase 1 percent per layer.