Phase separation within NiSiN coatings during reactive HiPIMS discharges: A new pathway to grow NixSi nanocrystals composites at low temperature

Abstract

The precise control of the growth nanostructured thin films at low temperature is critical for the continued development of microelectronic enabled devices. In this study, nanocomposite Ni-Si-N thin films were deposited at low temperature by reactive high-power impulse magnetron sputtering. A composite Ni-Si target (15 at.% Si) in combination with a Ar/N 2 plasma were used to deposit films onto Si(001) substrates, without any additional substrate heating or any post-annealing. The films microstructure changes from a polycrystalline to nanocomposite structure when the nitrogen content exceeds 16 at.%. X-ray diffraction and (scanning) transmission electron microscopy analyses reveal that the microstructure consists of nanocrystals, Ni x Si (x > 1) 7-8 nm in size, embedded in an amorphous SiN x matrix. It is proposed that this nanostructure is formed at low temperatures due to the repeated-nucleation of Ni x Si nanocrystals, the growth of which is restricted by the formation of the SiN x phase. X-ray photoelectron spectroscopy revealed the trace presence of a ternary solid solution mainly induced by the diffusion of Ni into the SiN x matrix. Four-probe electrical measurements reveal all the deposited films are electrically conducting.