The Defect Formation Mechanism Associated with Low Dose Implants into Si Fin Structures

This paper investigates the evolution of implant damage during the fabrication of isolation regions below FinFETs. To isolate p-type devices, 240 keV P+ 3.5 × 10
¹³
/cm
²
and 185 keV P+ 1.5 × 10
¹³
/cm
²
implants were done into Si fin structures that were nominally 6-8 nm wide and 120 nm tall. Recent reports have shown that these implants can created extended defects in the form of stacking faults in the fins upon annealing at 800°C in a furnace for 30 minutes if the oxide encapsulating the fins is left in place during the annealing. The combination of stress and implant damage was shown to reduce the threshold for defect formation. This paper shows that the implant damage evolves from point defect clusters to stacking faults between 600°C and 800°C. The evolution of the defects into stacking faults is not well understood. Once the stacking faults are observed they are stable even after annealing at 1000°C. The role of ion scattering from the oxide and oxygen recoil implantation into the fins is modeled using 2-D Monte Carlo simulations and the effect on defect formation and evolution is discussed. It is concluded that the combination of stress from the oxide and recoil damage to the fin results in a significant reduction in the defect formation threshold in fin structures.