Comparison of the properties of Cu films deposited on four different types of TiN substrates

Abstract

Cu is now widely accepted as the premier replacement for Al in ULSI interconnect metalliztion. However, it cannot be used without a diffusion barrier since it diffuses through a SiO₂ layer into the Si substrate very easily. TiN is one of the potential candidates for the barrier. In this paper the properties of the Cu films deposited on four different kinds of TiN films were compared. The properties of the CVD-Cu film strongly depend upon the type of the TiN substrate. The Cu film with the highest quality from the viewpoint of surface roughness and thickness uniformity on the four different kinds of the TiN substrate are obtained at 180, 220, 200°C and 200°C for the TiN(TDEAT), TiN(TDEAT+NH₃), TiN(TDMAT), and TiN (sputtered) substrates, respectively. The Cu deposition temperatures at which the Cu films with the lowest electrical resistivity are deposited 200°C on TiN(TDEAT), at 220°C on TiN(TDEAT+NH₃) and TiN(TDEAT) and 180°C on TiN(sputtered), respectively. The smoothest and flattest surface morphology of the Cu film is obtained on TiN(TDMAT), the next on TiN(TDEAT), the third on TiN(sputtered), and the last on TiN(TDEAT+NH₃) as a descending order at the Cu deposition temperatures of 200°C.