Selective atomic layer deposition of MoSix on Si (0 0 1) in preference to silicon nitride and silicon oxide

Abstract Highly selective deposition of MoSi x on Si in preference to SiO 2 and SiN x was achieved via atomic layer deposition (ALD) using MoF 6 and Si 2 H 6 at 120 °C. The selectivity was enabled by the lack of chemical reactivity between the reactants and the SiO 2 and SiN x substrates. In contrast, MoF 6 nucleated in a self-limiting manner on H-terminated Si, and a following Si 2 H 6 exposure reduced MoF x to Mo 0 which is consistent with Mo-Si bond formation. X-Ray photoelectron spectroscopy (XPS) revealed that the 5 ALD cycles of MoF 6 and Si 2 H 6 selectively deposited a substoichiometric MoSi 2 film on the Si substrate in contrast to previous results showing a nearly pure Mo deposition. Extra Si 2 H 6 doses on the substoichiometric MoSi 2 film incorporated more Si into the film without disturbing the inherent selectivity over SiO 2 and SiN x . A depth-profiling study showed that the bulk of the film has Si/Mo = 1.7–1.9 with 2 H 6 doses inducing silicide formation instead of metal deposition. To verify selectivity on the nanoscale, the selective deposition of MoSi x was investigated on a patterned Si wafer containing three-dimensional (3D) nanoscale SiO 2 and SiN x features. Cross-sectional transmission electron microscopy (TEM) showed that selective MoSi x deposition was achieved on nanoscale 3D structures. AFM documented that there were less than 10 nuclei/µm 2 on SiO 2 .; since SiO 2 has ∼10 6 /µm 2 OH groups, this corresponds to an intrinsic selectivity of about 10 6 :1 between the OH groups on SiO 2 and Si-H groups on Si. This inherent substrate-dependent selectivity for silicide deposition allows the elimination of pre-positioning of passivants.