Methods to lower the resistivity of ruthenium interconnects at 7 nm node and beyond

Abstract

36 nm pitch dual damascene interconnects are patterned and filled with ruthenium. Different adhesion layers are used to form the Ru interconnects. Ru line resistivity is measured by the temperature coefficient of resistivity method, and the area verified by TEM. Ru line resistivity is found to depend on the adhesion layer. The adhesion layers with higher intrinsic resistivities reduced the Ru line resistivity. A ∼10% Ru resistivity reduction can be achieved with ALD TaN or TiN adhesion layers or oxidized TaN, relative to PVD TaN. Grain boundary scattering may play an additional role, as demonstrated by different aspect ratio samples. The lowest Ru resistivity in these interconnects is 15 μω-cm, at a cross-sectional area of 300 nm2. Ru damascene metallization is extendible to features with critical dimension around 10 nm. Ru may match Cu line resistance for line dimensions below ∼17 nm.