Process Control for the Modification of Ruthenium Resistivity in Scaled Subtractive Interconnects

For advanced interconnect nodes, finding a new low-resistivity, barrier-independent material to replace copper becomes critical as pitch scaling reaches less than 20nm due to the poor scaling of barrier/liner films necessary for copper metallization leading to increased resistivity. Materials like ruthenium are promising replacement interconnects since they can be barrier-less and have good electrical properties at narrow wire dimensions. However, ruthenium film properties can vary depending on the underlayer and film deposition conditions. Optimization of the ruthenium deposition process is therefore necessary to provide a sufficient advantage over copper. Film grain size and orientation both impact resistivity, and the modification of these parameters is discussed and presented in this report.