TiN films by Atomic Layer Deposition: Growth and electrical characterization down to sub-nm thickness

This study reports on the growth and characterization of TiN thib films obtained by atomic layer deposition at 350-425 ◦C. We observe a growth of the continuous layers from the very beginning of the process, i.e. for a thickness of 0.65 nm, which is equivalent to 3 monolayers of TiN. The film growth stabilizes in a self-limiting surface-reaction mode represented by a constant growth rate of 0.02 nm/cycle. We further report on the resistivity of ultra-thin TiN films and its evolution with film thickness. The resistivity is determined by both optical spectroscopic ellipsometry and electrical techniques. The latter includes circular transfer length method and linear test structures. The resistivity increased significantly with decreasing film thickness below 4 nm, as well as the discrepancy between the optical and electrical method. This is attributed to the scattering effects of conduction electrons. Native oxidation of a few nm thick TiN films leads to non-linear I–V characteristics.