Co-sputtering Co–Ti alloy as a single barrier/liner for Co interconnects and thermal stability enhancement using TiN metal capping

Abstract

Scaling of interconnect dimensions is becoming increasingly difficult due to the fast rise in line/via resistance. To alleviate this problem, Co is a high-potential alternative material of Cu or W in metallization schemes. In this work, Co interconnects is imitated, where Co1−xTix is proposed as single barrier/liner to replace conventional thick TiN/Ti bilayer structure, reserving more available space for interconnect metal to achieve overall lower line resistance. The samples with and without Co1−xTix or TiN metal capping were fabricated in attempt to optimize the whole interconnects. Meanwhile, the properties of these films with different stacking structures were comprehensively studied through material analysis instruments. In order to further evaluate the barrier ability of Co1−xTix single layer, the capacitance–voltage (C–V) and current–voltage (I–V) characteristics of MOS capacitors after thermal stress (TS) as well as bias thermal stress (BTS) were analyzed elaborately. Obtained results indicate that Co1−xTix single barrier/line is effective to enhance adhesion property and to restrain Co diffusion into SiO2 dielectric, and TiN metal capping is also indispensable for Co interconnects to improve thermal stability and to prevent Co oxidation.