Improved reduction of contact resistance in NiSi/Si junction using Holmium interlayer

In this study, effect of Ho interlayer was investigated in nickel silicide (NiSi)/Si junction for contact resistance reduction. A thin Holmium (Ho) interlayer was applied to Ni/(p/n)-Si contact to reduce contact resistance between NiSi and Si. Thickness of 5 nm Ho layer was first deposited on As-doped n-type Si layer and BF₂-doped p-type Si layer, followed by in situ deposition of a 15 nm-thick Ni film and 10 nm-thick TiN film. After the formation of the NiSi by rapid thermal annealing (RTA) at 450 °C for 30 s, specific contact resistivity (ρ_c) between Ni-silicide and doped silicon region is extracted. There is a great reduction of the ρ_c, that is, from 9.84 × 10⁻⁵ Ω cm² to 1.16 × 10⁻⁵ Ω·cm² for n-Si and 6.24 × 10⁻⁵ Ω·cm² to 1.84 × 10⁻⁵ Ω·cm² for p-Si substrates, respectively. The improved interface morphology by introducing of Ho interlayer could be responsible for the ρ_c reduction.