Use of ErSi2 in source/drain contacts of ultra-thin SOI MOSFETs

The prospect of Erbium silicide (ErSi2) contacts for source/drain metallization in ultra-thin n-channel silicon-on-insulator (SOI) MOSFETs have been studied. Very thin layer of ErSi2 was formed on Si(001) by Er deposition followed by in situ annealing in the range of 400–600 °C under ultra-high vacuum (UHV) condition. The silicification process was found to depend on surface conditions prior to the Er deposition. The silicide layers were found to be stable up to a temperature of 700 °C. Good ohmic nature on n-type Si and well-defined rectifying behavior on p-type Si have confirmed a low electron barrier height at the ErSi2/Si contact. A simplified analysis based on transmission line modeling has been used to show that parasitic source/drain resistances of the order of 100 Ω μm or less can be achieved for SOI thickness of 10 nm.