Selective growth of tantalum nitride and hafnium nitride thin films on OTS patterned SI(100) substrates by MOCVD method

TaN and Hf₃N₄ thin films have been selectively deposited on Si(100) substrates in the temperature range of 400 - 500°C by combination of micro-contact printing (μCP) and metal-organic chemical vapor deposition (MOCVD) methods. The patterned Si(100) substrates were initially fabricated by μCP methods using octadecyltrichlorosilane (OTS) to form the self-assembled monolayers (SAMs). The compounds [Ta(NMeEt)₃(N ^tBu)] and [Hf(NEt₂)₄] were used as the precursors for the growth of TaN and Hf₃N₄ thin films, respectively. For a comparative study, we used the same deposition system and characterized the as-grown films with the same sequence using the instruments such as optical microscope, μ-Raman spectrometer, AFM, SEM/EDX, XRD, and alpha-step profiler. In both the cases of TaN and Hf₃N₄ film growth, we found that there are quite different growth rates between the film growth on the OTS patterned region and the clean silicon surface. In the beginning of deposition both nitride films prefer to grow on silicon surface rather than OTS patterned areas due to hydrophilicity of silicon surface. With increasing deposition time, however, we have found that the selectivity of TaN and Hf₃N₄ thin films depends on the deposition time. The reason is that above 400°C the hydrophobic characteristics of OTS SAMs surfaces can slowly change when the deposition time exceeds a certain period. Also C-V and I-V characteristics of Al / TaN /p-Si diode structures were measured. The dielectric constant and the leakage current density were approximately 4.6 and 10^-4 A/cm at over 2V, respectively, indicating that the deposited TaN thin film has a conductive characteristic.