Phase formation and electrical resistivity of ultrahigh vacuum deposited Cu thin films on epitaxial Si–Ge layers on Si and Ge

Abstract

The phase formation and the morphological stability of ε1-Cu3Ge and ε1-Cu3(Si1−xGex) in Cu/epitaxial-Ge(e-Ge)/(111)Ge, Cu/(001)Ge, Cu/e-Ge/(111)Si, and Cu/(001)Si–Ge alloys have been investigated by transmission electron microscopy in conjunction with the energy dispersive spectrometry as well as by sheet resistance measurement. Epitaxial Cu and epitaxial ζ-Cu5Ge were found to form in as-deposited Cu/e-Ge/(111)Ge and Cu/e-Ge/(111)Si. On the other hand, textured Cu was found to form in the other systems. Polycrystalline ε1-Cu3Ge and ε1-Cu3(Si1−xGex) were the only phases formed in 150–500 °C annealed Cu/Ge and (Cu/e–Ge/Si and Cu/Si–Ge alloys) systems, respectively. They were found to agglomerate at 550 °C. The room-temperature oxidation of substrate in the presence of Cu3(Si1−xGex) was found only in the Cu/Si0.7Ge0.3 system. From the sheet resistance measurement, ε1-Cu3Ge has the lowest resistivity of 7 μΩ cm after 400 °C annealing. The electrical resistivity was found to decrease with the Ge content.

Electrical and Microstructural Characterization of Cu-Germanide Contacts Formed on p-Type Ge Substrate

“…This indicates that the Cu-Ge system seriously suffers from thermal degradation at higher annealing temperatures. It is clear that Cu 3 Ge is the only phase formed at different RTA temperatures and that the Cu 3 Ge films starts to agglomerate at 550 °C and completely lose their structural integrity when annealed at 600 °C as reported by Borek et al and Lai et al (4,9).…”

“…Gaudet et al (12) carried out a systematic investigation of the thermally induced reaction of various transition metals with germanium and found that Cu reacts with germanium at extremely low temperatures and that it forms a low resistivity phase of Cu 3 Ge with a sheet resistance of 8.5 Ω/sq and that the germanide film degrades morphologically at temperatures of only 350 °C. Lai et al (9) investigated the phase formation and morphological stability of ε1-Cu 3 Ge in Cu/(001)Ge and found that polycrystalline ε1-Cu 3 Ge was the only phase formed in the annealing temperature range of 150 -500 °C and starts to agglomerate at 550 °C. Besides, its low resistivity, the successful demonstration of Cu-germanide as a contact material to Ge requires a complete understanding of the phase/microstructural evolution undergoing during rapid thermal annealing of Cu films on Ge.…”

“…Despite the advantages of Cu-germanides, there are no reports in the literature on the electrical properties of copper germanides to germanium. There were reports available on phase/microstructural evolution and electrical properties of Cu-germanide as a contact material in Si and SiGe based semiconductor devices (4,5,9). Cu-germanide is reported to be a potential candidate for contact and metallization for the next generation Si-based semiconductor devices.…”

The Discovery of Plasmon Resonance in Germanide Nanowires Grown on Cu Foil

“…Thus, researches of LSPR in different materials have gained much attention in recent years and the plasmonic property of Si and other materials has been discovered [15]- [17]. Manuscript Copper germanide (Cu 3 Ge) initially gained much attention for its extremely low resistivity, Ohmic contacts for p-and ntype GaAs substrates, low formation temperature (∼450°C), high oxidation resistance and chemically stability in air up to about 520°C, and great adhesion to SiO 2 [18]- [24]. The electrical properties make the Cu 3 Ge a promising candidate for contact and interconnect for future applications.…”