Electrical reliabilities of porous silica low-k films

Electrical reliability of self-assembled porous silica films was investigated. Vapor phase silylation by use of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) was developed to reduce silanol groups and enhance siloxane cross-linkage, resulting in achieving lower dielectric constant and higher elastic modulus. To promote siloxane cross-linkage, Cs ion was doped to its precursor solution. The self-assembled porous silica low-k film was integrated in Cu damascene interconnects with ultraviolet (UV) irradiation and TMCTS vapor treatment, resulting in the highest elastic modulus of 9 GPa with the dielectric constant of 2.1. Sidewall protection layer was formed in the trench for Cu interconnects to improve time-dependent dielectric breakdown (TDDB) lifetime of more than 10 years at the electric field of 2.3 MV/cm.