Direct Electrodeposition of Cu on Ru-Al2O3 Layer

This study introduces the direct electrodeposition of Cu on Ru-Al2O3 layers, which is a promising material to replace Cu seed, and Ta diffusion barrier layers at once. Ru-Al2O3 layers are deposited by atomic layer deposition (ALD), and their compositions are manipulated by varying the cycle numbers of Ru and Al2O3 ALD. The addition of Al2O3 induces the development of nanocrystalline Ru, instead of columnar structure, enhancing the characteristics as a diffusion barrier without losing a role of the seed layer for Cu electrodeposition. The native oxide of Ru is electrochemically eliminated by the coulometric reduction method (CRM) prior to Cu electrodeposition. The influences of both applied potential and the composition of Ru-Al2O3 layer on Cu film properties are clarified. Furthermore, the ability of Ru-Al2O3 layer to inhibit Cu diffusion is assessed, and it is confirmed that Ru-Al2O3 layer perfectly inhibits Cu diffusion during the annealing carried out at the temperature of 550 degrees C for 30 min with the layer thickness of 7.5 nm. (C) 2013 The Electrochemical Society. All rights reserved.