Copper contamination effects in 0.5 mu m BiCMOS technology

Copper is attracting increasing interest as a material for interconnections in future high speed ULSI circuits because of its low electrical resistivity and high electromigration performance [1]. Obviously, copper metallization has entered the stage of application in future ULSI fabrication [2]. However, the possibility of using for as long as possible the same processing equipments for the fabrication of circuits with either the standard Al-based or new copper metallization could be a major issue for circuit manufacturers. CMOS and bipolar test-circuits were used to detect the effects of Cu cross-contamination that could occur in equipment used for the fabrication of both Al-based and Cu interconnections. This paper describes the effects of such a contamination for typical thermal annealings used during backend processing. The diffusion barrier ability of a thin TiN film deposited at the backside of the Si substrate is also demonstrated.