Erbium germanosilicide Ohmic contacts on Si1−x Ge x (x=0–0.3) substrates

Abstract

We have studied erbium germanosilicide (ErSiGe) Ohmic contacts on n-type Si1−xGex substrates with differing Ge concentrations (0⩽x⩽0.3). Thin layers of Ti (20 nm)/Er (20 nm) were deposited on Si1−xGex substrates and then post-annealed at 600°C for 60 s to form a stable ErSiGe film. The structures of the ErSiGe films and ErSiGe/Si1−xGex interfaces were characterized by Transmission Electron Microscopy measurements (TEM). The TEM images showed that the thicknesses of ErSiGe films and the Si1−xGex substrates were about 60 and 50 nm, respectively. The ErSiGe/Si1−xGex structure had a smooth interface. Moreover, no agglomeration or Ge segregation was observed. The contact resistivity of the ErSiGe/Si1−xGex structures was measured by the specially designed four-terminal Kelvin structures. When the Ge concentration of Si1−xGex substrates increased from 10% to 30%, the specific contact resistivity (ρc) slightly decreased from 9.0×10−7 Ω·cm2 to 7.4×10−7 Ω·cm2, indicating that the Ge concentration is not the main effect on the ρc of the ErSiGe/Si1−xGex Ohmic contacts.