Ultra-Shallow Junction Formation by Monolayer Doping Process in Single Crystalline Si and Ge for Future CMOS Devices

Abstract

We focused on the damage-free monolayer doping (MLD) method starting from a chemical reaction of molecules on Si and Ge surfaces and applied it to 3D MOSFET device fabrication. MLD methods were verified by different material analysis, such as XPS and Raman spectroscopy. For a Si-based FinFET structure, compared to the device with ion implantation, the short channel effect of source and drain (SD) extension regions formed by MLD are improved. The shallower SD extension regions formed by low-temperature microwave annealing (MWA) are expected to the device showing better electrical properties than deeper ones formed by RTA. In addition, formation of the n- and p-type doping in Ge by MLD was also investigated. Even after annealing at 800°C for 300 sec by RTA, the p-type doping still exhibits a low surface doping concentration due to the low diffusion coefficient of B in Ge and surface diffusion limitations at the MLD/Ge interface. By using a combination of RTA and CO2 laser spike annealing (LSA), MLD n-type doping in Ge are formed with junction depths of ≈15 nm, and peak concentration of ≈ 6 × 1020 atoms/cm3. The dopant activation for the MLD-doped channels of Ge junctionless FinFETs (JLFinFETs) is improved after the additional CO2 LSA.