Ternary and quaternary Ni(Si)Ge(Sn) contact formation for highly strained Ge p- and n-MOSFETs

Abstract

The formation of new ternary NiGeSn and quaternary NiSiGeSn alloys has been investigated to fabricate metallic contacts on high Sn content, potentially direct bandgap group IV semiconductors. (Si)GeSn layers were pseudomorphically grown on Ge buffered Si(001) by reduced pressure chemical vapor deposition. Ni, i.e. the metal of choice for source/drain metallization in Si nanoelectronics, is employed for the stano-(silicon)-germanidation of highly strained (Si)GeSn alloys. We show that NiGeSn on GeSn layers change phase from welloriented Ni 5 (GeSn) 3 to poly-crystalline Ni 1 (GeSn) 1 at very low annealing temperatures. A large range of GeSn compositions with Sn concentrations up to 12 at.%, and SiGeSn ternaries with large Si and Sn compositions from 18%/3% to 4%/11% are investigated. In addition, the sheet resistance, of importance for electronic or optoelectronic device contacts, is quantified. The incorporation of Si extends the thermal stability of the resulting low resistive quaternary phase compared to their NiGeSn counterparts.

Process modules for GeSn nanoelectronics with high Sn-contents

“…The van-der-Pauw method [15] has been used to measure the sheet resistance of the so formed NiGeSn films. The lowest sheet resistance was obtained by stano-germanidation at 325°C [16]. The low-resistive NiGeSn-phase could be maintained over the complete available Sn-content range from 0 to 12.5 at.%.…”

Schottky barrier tuning via dopant segregation in NiGeSn-GeSn contacts

“…Thermal treatment in H 2 :N 2 forming gas at 325 C for 10 s led to the formation of 23 nm thick metallic NiGeSn poly-crystalline layers with low contact resistivity. 14…”

“…Mainly metal-Si alloys (i.e., silicides like NiSi, NiAlSi, and CoSi 2 ) but also metal-Ge alloys (i.e., germanides such as PtGe and NiGe) have been widely studied for different metals and doping species. 11,12 However, for Sn-based alloys there are only a few studies on nickel-stano-germanide (NiGeSn [13][14][15][16][17] and NiPtGeSn. 18 In those studies, Schottky barriers were modified with dopants such as boron atoms 15 or impurities such as sulfur and selenium atoms.…”

GeSn lasers for CMOS integration

“…The mesa and the contact areas are defined by optical lithography and reactive ion etching (Cl2/Ar plasma) followed by an Al2O3/SiO2 passivation. Finally, ~20 nm thick stanogermanide contacts [4] are formed. Figure 10 shows an SEM image of a processed LED.…”