Initial growth stage of nanoscaled TiN films: Formation of continuous amorphous layers and thickness-dependent crystal nucleation

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The initial growth stage of titanium nitride (TiN) deposited by reactive magnetron dc sputtering onto (111)-oriented Si substrates was investigated by using high-resolution transmission electron microscopy (HRTEM). During the initial growth stage, a continuous amorphous layer was observed when the deposited film was less than 1 nm thick. Crystal nucleation occurred from the amorphous layer when the film grew to about 2 nm thick. No preferred orientation was found for the initial crystal nuclei. The growth of the crystal grains depended on the N2 partial pressure, PN2. Increasing PN2 from 0.047 to 0.47 Pa enhanced lateral grain growth and coalescence between grains. For PN2=0.47 Pa, planar grains with a large lateral dimension were found formed by grain growth and coalescence, inducing a (200) film orientation. For films formed at PN2=0.47 Pa, an amorphous interlayer 1.5–1.8 nm thick formed between the TiN layer and Si substrate, and was indicated to be primarily SiNx by x-ray photoelectron spectroscopy and HRTEM. This interlayer was less than 0.5 nm thick in films formed at PN2=0.047 Pa.