FORMATION OF PTSI-CONTACTED P+N SHALLOW JUNCTIONS BY BF2+ IMPLANTATION AND LOW-TEMPERATURE FURNACE ANNEALING

Abstract

This work investigates the characteristics of PtSi-silicided p+n shallow junctions fabricated by implanting BF2+ ions into either the Pt/Si (ITM scheme) or the PtSi/Si (ITS scheme) structure followed by annealing in N2 furnace at temperatures from 650 to 800-degrees-C. For a structure with Pt film of 30 nm thickness or PtSi film of 60 nm thickness, the implantation energy ranges from 40 to 80 keV with a dose ranging from 1 x 10(15) to 1 x 10(16) cm-2. For the ITS samples with BF2+ implantation at 40 keV, all ions are confined in the PtSi layer; therefore, only a modified Schottky junction is formed by the diffusion of boron atoms from the PtSi film during the annealing. The junction depth may be as shallow as 30 nm from the PtSi/Si interface. A complete p+n junction is formed for the ITM samples with implantation at 40 keV as well as all the samples implanted at 80 keV. The junction thus obtained has a forward ideality factor lower than 1.02 and a reverse current density less than 0.2 nA/cm2 at -5 V. Activation energy measurement indicates that most of the implantation damages have been recovered after annealing at a temperature as low as 700-degrees-C. The reverse area and peripheral leakage current density are separated by measuring diodes of different perimeter/area ratio. For good samples, the reverse peripheral current comes from the surface generation current within the depletion region underneath the field oxide. All of the experimental results reveal that either Pt or PtSi film can be employed as an efficient barrier film in the ITM/ITS technique to form excellent and ultrashallow junctions with a low thermal budget.