Very low resistance CoSi2 formation by metal vapour vacuum arc implantation into SiO2/Si and Si3N4/Si structures

A metal vapour vacuum arc (MEVVA) implanter was used to form very low sheet resistance silicide CoSi2 in the structures of SiO2/Si and Si3N4/Si. Prior to Co implantation, wafers of Si (100) and Si (111) were covered with SiO2 and Si3N4 films to form SiO2/Si and Si3N4/Si structures. The metal ions of Co were implanted into Si, SiO2/Si and Si3N4/Si structures at an energy of 40 keV and doses of (0.5–1.0)×1018/cm2. After Co implantation, the samples were annealed at 800–950°C for 10–30 s in ambient N2. The sheet resistance R□ was measured for each samples before and after annealing. The R□ was 10–60 Ω/□ before annealing and 0.4–9.0 Ω/□ after annealing. Excellent silicide CoSi2 films with very low sheet resistance R□<0.5 Ω/□ were obtained on the SiO2/Si and Si3N4/Si structures. The sheet resistance R□ of CoSi2 using the SiO2/Si and Si3N4/Si structures is less than one to two orders than the R□ of CoSi2 using the Si wafers directly. The excellent silicide CoSi2 films with very low resistivity have a great advantage for use in VLSI-CMOS technology. Time-of-flight energy elastic recoil detection (ToF-EERD) analysis was used to measure the depth distributions of O, N, Co and Si. The SiO2 and Si3N4 films were almost sputtered away after Co implantation into SiO2/Si and Si3N4/Si structured wafers. The ERD results proved that these sacrificial films of oxide or nitride as protective films can be used to reduce sputter erosion and roughening in high dose metal implantation of silicon, resulting in excellent electrical properties.