Improvement of copper diffusion barrier properties of tantalum nitride films by incorporating ruthenium using PEALD

Abstract

Ru-incorporated TaN (Ru-TaN) films were investigated as a Cu diffusion barrier material. Ru-TaN films were prepared by sequential deposition of Ru and TaN using plasma-enhanced atomic layer deposition (PEALD). The film composition was controlled by the number of Ru unit cycles. While the resistivity of Ru-TaN films was increased abruptly at low Ru composition (similar to 0.06), the resistivity of Ru-TaN films was decreased gradually as the Ru composition increased after that composition. The crystal structures of Ru-TaN films were amorphous at the Ru composition range from 0.19 to 0.52 due to disturbance of grain growth. However, the Ru-TaN films had TaN-like structure below this range and Ru-like structure above this range. The amorphous Ru-TaN films had nanocrystallite embedded structure in an amorphous matrix. This amorphous Ru-TaN barrier showed a better Cu diffusion barrier property (similar to 700 degrees C) than the TaN barrier (similar to 650 degrees C) because the Cu diffusion through the grain boundary was suppressed by the amorphization. In addition, the Ru-TaN barrier exhibited good adhesion to both Cu and SiO(2). (C) 2008 The Electrochemical Society.