Narrow CoSi/sub 2/ line formation on SiO/sub 2/ by focused ion beam

We propose a technique for formation of CoSi/sub 2/ line structures on SiO/sub 2/ films, which utilizes irradiation with 40 keV Si/sup 2+/ FIB to the Co (14 nm)/Si (50 nm)/SiO/sub 2/ (20 nm) stacked layer structures. Ion irradiation was performed at room temperature (RT) in order to prevent the thermal formation of cobalt silicide in regions without irradiation. After ion irradiation, unreacted Co layers remaining on the surfaces were removed by dipping the samples into the solution of HNO/sub 3/:H/sub 2/O/sub 2/=1:3, and unreacted Si layers were removed by H/sub 3/PO/sub 4/ at 160/spl deg/C. The hot H/sub 3/PO/sub 4/ removes the deposited Si without etching the irradiated regions or SiO/sub 2/ films. After the etching, the samples were heat treated at 700 and 900/spl deg/C for 20 min. As a result, cobalt silicide line structures were formed. The resistivity evaluated for samples heat treated at 700 and 900/spl deg/C was in agreement with that of CoSi and CoSi/sub 2/, respectively. CoSi/sub 2/ line structures with less than 200 nm width can be made by the procedure.