Healing of voids in the aluminum metallization of integratedcircuit chips

A thermal treatment for healing voids in the aluminum metallization of integrated circuit (IC) chips has been discovered. The aluminum metallization is alloyed with nominally 1 wt.% of silicon. This discovery arose from efforts to cause further growth of preexisting voids in IC RAMs intended for long-term unattended spacecraft applications. The experimental effort was intended to cause further void propagation for the purpose of establishing a time/temperature propagation relationship, but it resulted instead in a healing of the voids. The thermal treatment consisted of heating IC chips with voids in the aluminum/silicon metallization to temperatures in excess of 200°C, followed by quick immersion into liquid nitrogen. The thermal treatment is described, and a theory based on silicon solubility and migration in aluminum is advanced to explain both the formation and the healing of voids in the aluminum metallization of IC chips