| 초록 |
Ruthenium (Ru) has been considered as one of the most promising materials for capacitor electrodes of gigabit-scale dynamic random access memory device due to its low electrical resistivity, easiness in dry etching process, and the capability of metal organic chemical vapor deposition process (MOCVD), which provides an excellent conformality onto a 3-D concave structure. However, there are few reports about the thermal stability of Ru thin films on TiN substrate and SiO2 substrate where the bottom electrodes should be deposited for capacitor application. In this study, the effects of annealing process on the thermal stability of Ru films deposited by MOCVD on the two types of substrates were investigated, which elucidate the correlation between various process parameters and agglomeration behavior of Ru films with/without capping dielectric layers. The 30 nm-thick Ru thin films without capping layer was thermally stable under Ar and H2 annealing ambient up to 600oC, while oxidation of films has occurred in the O2 surroundings even at 500oC which results in the rough surface morphologies of deposited films on TiN substrate. On the other hand, Ru films grown on SiO2 surface was more thermally stable than those on TiN surface under the same experimental conditions due to the difference in surface and interface energy between the Ru and substrates. The thermal stability of Ru films was increased by the adoption of capping dielectric layer such as Al2O3, which suppressed the void formation and lessen the agglomeration of thin Ru films because of the decrease in surface energy. These results represented the enhanced thermal stability of dielectric layer/Ru film stacks during the post-annealing process. |
