A Study on AlCu with ALPS Al and Glue layer on Electromigration

Abstract

It has been reported, that EM lifetime of Ti/Al-Cu structure is shorter than that of Ti/TiN/Al-Cu structure. Our study shows that the lifetime of Ti/ALPS Al-Cu structure is better than Ti/TiN/ALPS Al-Cu. In this paper, we will discuss the effect of the Glue layer -Ti/TiN & Ti, and the effect of the AlCu processes-Hot Al and ALPS/Hot Al to explain the main reasons. After the study, we found Ti /ALPS/Hot Al-Cu has the best EM lifetime and we believe it’s due to (1) The ALPS process has less Cu precipitation at the interface between Al and Ti/TiN, which makes Cu more concentrated in the AlCu layer (2) The Glue layer of Ti forms TiAl3, and these intermetallic compounds changes the AlCu ratio. The Al atomic ratio decreases, while the Cu atomic ratio increases .The formation of Ti3Al intermetallic compounds increased the Cu concentration in the grain boundary of AlCu metal line and affected the EM result.