Activation improvement of ion implanted boron in silicon through fluorine co-implantation

Abstract

In this study, boron diffusion and activation characteristics of samples implanted with F co-implantation were studied to meet the challenge of lower sheet resistance. Samples were implanted with F co-implantation in a dose range of 0 ͑no F͒ to 5ϫ10 15 cm Ϫ2 , at a fixed energy of 25 keV, followed by 950°C/10 s rapid thermal annealing. It was found that although the fluorine has a negligible affect on the boron diffusion at the specified conditions, a higher F dose reduced the boron sheet resistance. Using reverse modeling, the boron solid solubility at 950°C was extracted as function of the F co-implant concentration. For low fluorine doses (0 -1ϫ10 14 cm Ϫ2 ), the boron solid solubility is similar to that reported in the literature (9ϫ10 19 cm Ϫ3 ). At higher doses, boron solid solubility increased by 25% and even 50% for F co-implantation doses of 1ϫ10 15 and 5 ϫ10 15 , respectively. We suggest that the F co-implantation terminates some of the defects created by the implantation, inactivating the defects and improving boron activation.

Low Temperature Dopant Activation for Integrated Electronics Applications

“…This technique appears to successfully reduce TED [8] and enhance boron activation [9]. However in certain cases the junction integrity is inferior to junctions formed using BF2 molecular implants or pre-amorphization with 74Ge or 28Si [7].…”

“…The use of 19F & "B co-implants have been investigated by a number of research groups, mostly in the context of suppressing ion-channeling and TED using low-energy implants along with high temperature /short time RTA [7][8][9]. This technique appears to successfully reduce TED [8] and enhance boron activation [9].…”

“…In most cases, SIMS and SRA profiles are used for a graphical representation of the data for comparisons between total (chemical) and electrically active dopant profiles, and relative comparisons between treatment combinations. Due to the number of samples involved in this study, and the desire for consistency in the evaluation of dopant activation, an approach referred to as reverse modeling [9] has been used to quantify the percentage of dopant activated. As the name suggests, reverse modeling takes a modeled profile that has been adjusted to yield the results of an actual measurement in order to "back out" the value of, in this case, the active dopant dose.…”

Solar‐grade boron emitters by BF3 plasma doping and role of the co‐implanted fluorine

“…Fluorine bubbles may also be trapped in some cases . However, according to other works, fluorine may inhibit (or may dissolve) the formation of EOR DL, by reducing available silicon interstitials . Moreover, a chemical fluorine–boron interaction may cause a boron diffusion retardation , while boron exodiffusion would also be enhanced in the presence of fluorine .…”

Influence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions

“…The assessment of the electrical dopant activation ͑total active dose or maximum active concentration͒ of a junction is often based on the combination of the chemical dopant concentration profile ͓measured by secondary-ion-mass spectroscopy ͑SIMS͔͒ and junction sheet resistance ͑obtained by four point probes measurements͒, [10][11][12][13][14] in which it is systematically assumed that the mobility versus concentration relations 15,16 are valid. However, nowadays junctions systematically contain a large amount of BICs that may act as additional scattering centers and have an impact on the carrier mobility.…”