Remote Plasma Atomic Layer Deposition of CO_3O_4 Thin Films

摘要

Cobalt oxide has been deposited with remote plasma ALD over a wide temperature window (100 - 400 °C), using CoCp_2 as cobalt precursor and with a remote O_2 plasma as oxidant source. This novel combination resulted in the deposition of high density (6.2 g/cm~3), stoichiometric Co_3O_4 with an electrical resistivity between 0.5 and 5.3 Ω cm. Several merits have been identified for this process. Compared to the literature, the temperature window was widened to 100 - 400 °C and the growth per cycle was higher at 0.05 nm/cycle, almost independent of the substrate temperature. Investigation of the material properties revealed cubic Co_3O_4 films with a preferential (111) direction for all temperatures with an increasing crystallinity with temperature. Furthermore, the plasma assisted process resulted in smooth Co_3O_4 films with a roughness of ≤ 1 nm for all substrate temperatures and film thicknesses (5 - 65 nm) investigated. Mass spectrometry measurements reveal a combustion-like reaction process.