ADHESION OF COPPER WITH DIFFUSION BARRIER LAYER FOR COPPER INTERCONNECTION

Abstract

Adhesion of copper with diffusion barrier layer has been studied for Cu interconnection. Ta-based barrier materials have been employed. The Cu adhesion property with these barrier materials was estimated by stress concept, and was experimentally examined. Higher and high stresses are attained in thin Cu layer (10 nm thick) when deposited on TaN and Ta diffusion barrier layers, which lead to poorer and poor adhesion strengths with Cu, respectively. On the other hand, much lower stress are attained in the thin Cu layer when deposited on TaSiN diffusion barrier, revealing much better adhesion strength of Cu with TaSiN layer. X-ray diffraction spectra and scanning electron microscopy measurement revealed that the highly stressed thin Cu layer on TaN barrier layer changes to a low stressed thin Cu layer as a result of agglomeration, which happened after annealing at 400 °C. The surface of thin Cu layer changes to rough surfaces with annealing at 400 °C in the layer deposited on TaN. However, a smooth surface is held in the low stress layer on the TaSiN barrier layer.