An Effect of Dopants on Contact Electromigration

Abstract

Recently, device reliability has been an important issue since the design rule is scaled down and complicated processing is involved. To improve the reliability, many problems should be solved. One of the problems in interconnection failure is short or open circuits at interconnection lines. Contact or via hole failure has been ignored while the metal line failure has been strongly studied by many researchers.In this study, electromigration (EM) phenomena at the submicron size of contact hole are presented with respect to the type of dopants, boron and arsenic, implanted by high dose. In both cases, the failure mode at the contact hole, the values of the activation energy and the mean-time-to-failure (MTTF) are much different. For example the value of MTTF in boron is lower than that in As. The contact failure by EM is analyzed by SEM micrographs, FIB micrographs, EM measurement. One of the interesting results is void formation at the interface between implanted surface and silicon dioxide film, which is located between contact holes. This fact indicates that the interface migration of Si is much faster than the self-diffusion of Si because the current path is mainly formed along the interface.