Ultra thin CVD TiN layers as diffusion barrier films on porous low-k materials

Abstract

In this work CVD TiN diffusion barriers were investigated for integration with porous ultra low-k (ULK) dielectrics. Sheet resistance measurements of thin CVD TiN films on capped porous ULK and a SiO2 reference were compared. The impact of different ULK material pore size (3 and 7 nm) on TiN diffusion barrier integrity was investigated for patterned structures by etch dip test and analytical methods. In addition a SiO2 CVD liner was used for pore sealing. It was detected that a smaller pore size facilitates a better CVD liner and TiN barrier formation which results in a better barrier integrity. Evaluation of barrier continuity by HF dip test showed no effect of the CVD liner for the ULK material with higher pore size. A remarkably decrease of the number of defects was observed compared to non-patterned samples. Also a reduced TiN penetration into the ULK compared to non-patterned samples was detected by EDX line scan. It is assumed, that a partial pore sealing during ULK etching using a photoresist mask occurred by formation of a passivation layer at the sidewall. Furthermore for lower pore size material the CVD liner improved the barrier performance.