Formation of NiSi-Silicided p⁺n Shallow Junctions by BF₂ ⁺ Implantation into/through Silicide and Rapid Thermal Annealing

Abstract

NiSi-silicided p+n shallow junctions are fabricated by BF2 + implantation into/through a thin NiSi silicide layer, followed by rapid thermal annealing (RTA). The NiSi film starts to show agglomeration after RTA at 650°C, which may result in the formation of discontinuous islands at higher temperatures. The incorporation of fluorine atoms in the NiSi film can retard the film agglomeration, making the film stable up to 800°C. A forward ideality factor very close to unity and a reverse bias current density of 0.6 nA/cm2 can be attained for the NiSi(31 nm)/p+n junctions fabricated by BF2 + implantation to a dose of 5×1015 cm-2 at 35 keV, followed by RTA for 30 s at 650°C; the junction formed is about 37 nm measured from the NiSi/Si interface. Activation energy measurement shows that the reverse bias junction currents are dominated by the diffusion current, which indicates that most of the implanted damage can be recovered by RTA at temperatures as low as 650°C.

Narrow Line Effect of Nickel Silicide on p+ Active Lines and Its Suppression by Fluorine Ion Implantation

“…In order to overcome these problems, it has been reported that fluorine is one of the most effective atoms for improving the thermal stability of silicide. [5][6][7][8][9][10][11][12][13] In fact, regarding nickel silicide, the suppression of the reverse bias leakage current at an n þ /p junction by fluorine implantation has been reported. 12,13) The chemical incorporation of fluorine into the NiSi phase near the interface strongly suppresses Ni diffusion, and as a result, the agglomeration of NiSi and the increase in reverse bias leakage current is suppressed.…”

“…12,13) The chemical incorporation of fluorine into the NiSi phase near the interface strongly suppresses Ni diffusion, and as a result, the agglomeration of NiSi and the increase in reverse bias leakage current is suppressed. [5][6][7]12,13) However, the effects of this superior technique on the narrow active lines and areas within 65-nm-node CMOS devices have not been investigated. For reliable CMOS devices using nickel silicide, the formation of stable NiSi on narrow active lines and areas, which are used as the S/D of the transistors or resistors of the devices, is important.…”