Effect of CoWP cap thickness on via yield and reliability for Cu interconnects with CoWP-only cap process

Abstract

Via resistance and stress migration lifetime were characterized for a CoWP-only cap process (i.e. no dielectric cap) and a CoWP+SiN cap process. For the CoWP-only process, the via resistance and stress migration lifetime depended on the CoWP thickness. In order to achieve a tightly distributed via resistance and long stress migration lifetime, the data suggests that the CoWP must be sufficiently thick to protect the Cu during the via etch and strip processes.