(A) study on the plasma-enhanced atomic layer deposition of RuTiN thin films

Abstract

Copper (Cu) has been used as a interconnection metal to enhance operating speed and reliability due to its lower electrical resistivity and high electromigration (EM) resistance compared with aluminum (Al). Since, however, Cu can quickly diffuse into Si and $SiO_2$ substrate and causes serious performance degradations of the semiconductor device, the suitable diffusion barrier of Cu is required. As the device feature size shrinks, the existing barrier materials are facing the limitation owing to relatively high resistivity and poor adhesion to Cu in the copper interconnection. Ruthenium (Ru) has been aroused with great concerns as Cu diffusion barrier because of its good electrical conductivity, good adhesion property to Cu, and immiscibility with Cu. However, Ru thin film was revealed to have some unfavorable characteristics for the application of Cu diffusion barrier such that it grows as columnar structure which provides a fast diffusion path for Cu and that it shows a poor adhesion to $SiO_2$. In order to exhibit a sufficient performance even at thinner film thickness, these undesirable properties must be improved. To address this issue, as a novel copper diffusion barrier material, the RuTiN thin films by plasma enhanced atomic layer deposition (PEALD) was suggested for the first time using bis(ethylcyclopentadienyl)Ru $[Ru(EtCp)_2]$ as Ru precursor, TDMAT (Tetrakis dimethyl amino titanium) $[Ti(N(CH_3)_2)_4]$ as TiN precursor. $N_2+H_2$ plasma and $N_2$ plasma was used as a reactant gas for Ru and TiN, respectively. And we also showed that RuTiN film by PEALD has so good properties that it would be a potential alternative diffusion barrier material for Cu. As a preliminary experiment, the growth characteristics of each Ru and TiN thin film by PEALD were studied for determining the PEALD process window. Ru film having resistivity of about 13μΩㆍcm was deposited with the saturated deposition rate of 0.039nm/cycle at a growth temperature of 200℃. TiN ...