Utilizing H2S to sulfurize transition metal and oxide barriers for suppressing resistivity scaling of ruthenium metallization

Abstract

Ruthenium is of great potential for use as next-generation interconnect metallization but still suffers from resistivity scaling at nanoscale linewidths due to the severe interface scattering of electrons. In this study, a thin sulfurized layer was hence formed on titanium-tantalum and titanium-tantalum oxide barriers by utilizing hydrogen sulfide gas for interface modification. The microstructure, chemical composition, bonding configuration and interfacial adhesion of the sulfurized barriers and ruthenium films were investigated, and the resistivity scaling of the ruthenium films on the barriers was evaluated. Experimental results indicate that an amorphous sulfide layer of only several nanometers thick was uniformly formed on the top surface of the barriers and changed the resistivity and binding state of the metal and oxide barriers. Attributed to the formation of the sulfide layer, the specular scattering of electrons at the ruthenium/barrier interface was enhanced, effectively suppressing the resistivity scaling of the ruthenium films, and the interfacial adhesion strength was also markedly improved.