Shallow source/drain extensions for pMOSFETs with high activation and low process damage fabricated by plasma doping

Abstract

Low sheet resistance and extremely shallow profiles are achieved by plasma doping with low process damage and high activation efficiency. High performance pMOSFETs have been also fabricated by taking advantage of wellcontrolled plasma doped extensions.Linear transconductance (Gm) of the pMOSFET with plasma doped extensions is about 30% larger than that of 10 keV ion implanted device with same source/drain junction depth.

Recoil implantation method for ultrashallow p+/n junction formation

“…This implies that the deposited energy distribution can be used to predict the knocked-in B dose. The predicted B doses reach maxima of about 3.6ϫ10 15 and 3.8ϫ10 15 cm Ϫ2 for B layer thicknesses of 10 and 17 nm with 20 and 40 keV Ge implants, respectively. It is desirable to maximize the recoil yield or the ratio of B dose to Ge dose for higher throughput.…”

“…The thicknesses of the B films thicker than 10 nm were measured by profilometry, while the thicknesses of the B films thinner than 10 nm were estimated from the measured deposition rate. 74 Ge ϩ was implanted at 20 or 40 keV at 7°with a dose of 3ϫ10 14 or 1ϫ10 15 cm Ϫ2 . Following the implantation, the remainder of the boron layer was etched away by a hot nitric acid dip.…”

“…Figure 4 shows the effects of anneal, Ge dose, and Ge energy on as-recoiled and annealed B profiles. The junctions were formed by 15 nm B layer deposition, 20 or 40 keV Ge implant at a dose of 3ϫ10 14 or 1ϫ10 15 cm Ϫ2 , and an anneal at 950 or 1050°C for 10 s.…”

“…For the 20 keV, 1ϫ10 15 cm Ϫ2 Ge implant, the 950 and 1050°C anneal resulted in sheet resistance of 550 and 200 ⍀/sq, respectively. The annealed B profiles have humps that do not appear in the as-recoiled B profiles.…”

“…27 Therefore, it is likely that the knocked-in B dose is proportional to the energy deposited at the B/Si interface via nuclear collisions by implanted Ge ions. Figure 5 compares the variations of the experimental knocked-in B dose and simulated deposited energy profile as functions of B layer thickness for 10 15 cm Ϫ2 Ge implants at 20 and 40 keV. The B dose was estimated from the asrecoiled B SIMS profiles.…”