Nucleation Behavior and Growth Characteristics of Atomic-Layer Deposited Iridium Thin Films with Ticp and Oxygen

Abstract

Platinum group elements (Pt, Ru, Pd, Rh, Ag, Au, and Ir) have excellent properties of high thermal and chemical stability, and low electrical resistivity. Due to the attractive characteristics, these materials are also expected for applications in the semiconductor industries. In particular, iridium (Ir) has attracted interests as a potential electrode for memory devices because of its high work function and low resistivity (bulk: 4.7 μΩ cm).Despite the advantages of Ir, the deposition of Ir thin films for the next-generation memory applications faces critical challenges. Since metal has a high surface energy, it is difficult to adsorb on a surface with a lower surface energy. So, formation of metal nuclei is delayed in the initial growth of atomic layer deposition (ALD), and island growth is preferred. During the ALD, sparsely grown nuclei cause an increase in surface roughness which deteriorates the leakage current properties of capacitors.In this study, we attempted ALD of Ir films from newly synthesized tricarbonyl (1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl iridium and oxygen. The growth behavior and film properties of impurity contents and bulk resistivity were investigated in terms of the growth temperature. Also, we examined the changes in the surface morphology of the iridium film with the film thickness. Consequently, we achieved the growth of continuous and smooth Ir films even below 4 nm by forming nucleation-promoting layer at high temperature and followed by ALD of Ir at low temperature. In addition, the capacitor device characteristics were also investigated using Ir as a bottom electrode.