STUDY OF THE THERMAL-STABILITY AT THE CU SIOF INTERFACE/

For future interconnect technologies several material changes are requ ired. Low-k dielectrics in combination with copper should offer the mo st efficient structures for interconnection. In this paper we have eva luated for the first time the compatibility of Cu and SiOF. An obvious advantage of SiOF is its similarity with SiO2 and therefore its abili ty to be easily integrated into MLM architectures. Different MIS struc tures, Cu/Barrier layer or not/SiOF/Si substrate, were formed to study the stability of the SiOF/Cu interface as a function of the temperatu re and electrical field applied. Ti and TiN thin films were used as ba rrier layers. Electrical (C-V and G-V measurements) and analytical cha racterizations (SIMS) have been performed. In the absence of a barrier neither Cu diffusion within SiOF nor F diffusion into Cu was detected by electrical measurements, even after annealing at 500 degrees C for 10 h. Moreover, positive mobile charges were not detected under a BTS stress of (3 MV/cm, 250 degrees C). The result would indicate that Cu diffusion into SiO2 is dramatically reduced by F dopant. In the case of Ti and TIN in contact with SiOF, SIMS profiles show clearly fluor d iffusion in the barrier layer.