The main issue of Cu metallization is the electromigration of Cu through the interface between Cu and the barrier or capping layer. To improve electromigration resistance at the Cu and barrier metal interface, insertion of a glue layer which enhances the adhesion of Cu onto the under layer may be effective. The wettability of Cu on Ru and Ta glue layers was evaluated as the index of Cu adhesion strength onto glue layers. The wetting angle of Cu (43°) on a Ru substrate was three times lower than that of Cu (123°) on a Ta substrate after annealing. Lower wetting angle of Cu on a Ru substrate indicates a good adhesion property between Cu and Ru and may imply a high electromigration resistance. The better Cu wettability of Ru compared to Ta can be explained by the concept of lattice misfit. A Ru(002) plane has lower lattice misfit, which suggests lower interface energy, and enhanced the adhesion of Cu onto Ru. However, the Ru film showed poor Cu diffusion barrier properties, which suggests Ru should be used as a glue layer in combination with another barrier layer.

No abstract

No abstract

The electromigration resistance of ultra-large scale integration (ULSI) Cu interconnects can be improved by inserting an adhesion promoter between Cu and the diffusion barrier. A metallurgical survey was accomplished to select the element having a good Cu adhesion property. For adoption as an interconnect material, it should have a low resistivity and should not react with Cu to avoid increasing the resistance of Cu interconnects. Ru, Os, Mo, W, and Ta satisfied the above conditions. The Cu adhesion property of these elements was estimated by the lattice misfit concept. The Cu adhesion property was experimentally examined and compared hcp elements (Ru and Os), which have a good matching interface with fcc Cu, with the bcc elements (Mo and Ta). Ru and Os, which had lower lattice misfit values, showed a better adhesion property than the bcc elements having higher lattice misfit values. Among these elements, Ru had the best Cu adhesion property and thus it can be an optimum glue layer element for Cu interconnects.

Articles you may be interested inAtomic layer deposition of ultrathin platinum films on tungsten atomic layer deposition adhesion layers: Application to high surface area substrates J. Vac. Sci. Technol. A 33, 01A130 (2015); 10.1116/1.4901459Low temperature hydrogen plasma-assisted atomic layer deposition of copper studied using in situ infrared reflection absorption spectroscopy Hot-wire-assisted atomic layer deposition (HW-ALD) has been identified as a successful method to form high quality metallic films using metallocene and NH 3 . A cobalt film formed by HW-ALD using cobaltocene and NH 3 was successfully demonstrated. The authors have elucidated the mechanism of HW-ALD during the precursor feed period and the reducing period. In the case of cobalt, a deposition temperature above 300 C is needed to avoid an inclusion of carbon impurities. This is because the physisorbed species are involved during the precursor feed period. NH 2 radical promotes the dissociation of the carbon-metal bond during the reducing period. This is examined by elucidation of the gas-phase kinetics, estimation of the surface reactions by quantum chemical calculations, and analysis of the exhaust gas using a quadrupole mass spectrometer.