Direct metal etch of ruthenium for advanced interconnect

In this work, Ru wires patterning by direct etch are evaluated for a potential 5 nm technology node. The characteristics of Ru etching by varying the bias voltage, total flow rate and Cl-2/(O-2+Cl-2) gas flow ratio are studied in an inductively couple plasma etching chamber. Ru sidewalls profile with a tapering angle of 90 degrees and Ru to SiO2 hard mask etch selectivity of 6 are achieved. The authors show the feasibility of patterning lines with an aspect ratio up to 3.5 and lines with a critical dimension down to 10.5 nm (with a 3 sigma line width roughness of 4.2 nm), which paves the way to further scaling of this approach. Finally, the authors present a study on Ru line roughness after patterning on 300mm wafers. Here, they compare line roughness results of wafers where Ru is deposited with different deposition techniques, such as atomic layer deposition and plasma vapor deposition, and it is annealed after deposition at various temperatures. Published by the AVS.