Fifteen-Nanometer Ru Diffusion Barrier on NiSi/Si for a sub-45 nm Cu Contact Plug

Abstract

A ruthenium film on a NiSi/Si substrate was evaluated for barrier performance in Cu contact metallization. The films were deposited by magnetron sputtering using Ni, Ru, and Cu targets. The low-resistivity NiSi film was initially produced from an Ni/Si substrate, and Ru and Cu films were sequentially deposited on the NiSi/Si substrate so that barrier performance could be studied. Barrier properties were elucidated by four-point probe measurement, x-ray diffractometry, scanning electron microscopy, Auger electron spectroscopy, and transmission electron microscopy. The stability temperatures of 600°C (Cu/NiSi/Si) and 650°C (Cu/Ru/NiSi/Si) were systematically verified and are discussed. Structural analysis indicated that the failure mechanism involved penetration of the Cu through the Ru/NiSi stacked film at a specific temperature, which induced the accelerated dissociation of the NiSi. Interposition of an Ru layer between the Cu and the NiSi/Si effectively prevented intermixing and substantially improved the thermal stability in the Cu/NiSi/Si stack films.

Improved Diffusion Barrier Properties and NiSi Thermal Stability for the Cu Contact with the Ru/TaSiN Stack on NiSi/Si

“…[1][2][3][4] The performance of Ta/TaN, TaN/Ta, Ru and Ru/TaN as barrier stack has also been demonstrated in the copper contact technology. [5][6][7][8][9] The requirements for diffusion barrier in the Cu contact structure are very critical since the barrier will be directly deposited onto the NiSi over the heavily doped junction area. The whole system should have not only excellent diffusion barrier properties but also good NiSi thermal stability, and the adhesion between barrier and NiSi should also be addressed.…”