Enabling Low Contact Resistivity on n-Ge by Implantation After Ti Germanide

The process to form Ti germanide on P-implanted Ge (2 x 10¹⁹ cm^-3) with low contact resistivity (ρc) was developed. Sequential deposition of Ti and TiN on n-Ge without annealing leads to rectifying I-V characteristic due to Fermi level pinning. With 600 °C annealing, Ohmic-like I-V behavior was achieved due to Ti germanide (C54 phase included) formation that depins Fermi level and makes ρ_c of 1.5 x 10^-5 Ω - cm² and Schottky barrier height for electron (Φ_BN) of 0.22 eV. Even for 700 °C annealing, the Ti germanide exhibits comparable ρ_c and good thermal stability without agglomeration, which is a concern of NiGe. By adopting additional P implantation after germanide, ρ_c and ΦBN can be further improved to 3.6 x 10^-6 Ω-cm² and 0.17 eV, respectively. The improvement is ascribed to the enhanced dopant segregation at the germanide/Ge interface that results in stronger dipoles and more significantly reduced Φ_BN and ρ_c. The Ti germanide process paves a promising path to enable a next-generation Ge technology.