High conductivity copper-boron alloys obtained by low temperature annealing

The electrical behavior during annealing of copper films with a nominal con centration of 2 at.% boron has been investigated. The evolution of the resi stivity of the film was monitored using an in situ technique, in which the film was ramp-annealed at constant ramp rates. At a temperature of 150-200 degreesC, the resistivity of the Cu(B) undergoes a first drop. This is foll owed by one or two such drops in resistivity, so that after completion of a ramp-anneal from 50 degreesC to 750 degreesC, the room temperature resisti vity decreases from the initial value of 13 mu Omega cm to 2.1 mu Omega cm, close to that of bulk copper. Isothermal annealing of the film also leads to substantial decreases in resistivity, from 13 mu Omega cm to 3 mu Omega cm after annealing at 350 degreesC for 8 h and to 2.5 mu Omega cm at 400 de greesC for 4 h. These results show that a dramatic reduction in resistivity of Cu(B) alloys takes place at temperatures below 400 degreesC, suggesting possible applications for silicon device interconnections.