FOCUSED ION-BEAM INDUCED DEPOSITION OF PLATINUM

Focused ion beam induced deposition of platinum from a precursor gas of (methylcyclopentadienyl)trimethyl platinum has been demonstrated. This organometallic compound is solid at room temperature with a vapor pressure of 0.054 Torr. Ga+ ions at 30-40 keV have been used. The resistivity and composition of the film and the deposition yield have been measured as a function of ion current density, line dose, substrate temperature, geometry, and supplemental hydrogen pressure. Yield varies from 0.2 to 34, and resistivity varies from 70 to 700 mu-OMEGA cm depending on the conditions. The resistivity and content of the carbon impurity are reduced as the ion current increases: the lowest resistivity is observed at the highest current density corresponding to 0.222 nA at scan speed 500 cm/s repeated over a 350 mu-m long line. The minimum linewidth achieved so far is 0.3 mu-m. Transmission electron microscopy shows the Pt film to be amorphous, and Auger analysis gives the film composition 46% Pt, 24% C, 28% Ga, and 2% O. The addition of hydrogen gas supplied to the same area by a second nozzle is found to have little effect on yield or resistivity. Although the deposition of gold from an organometallic precursor on a substrate at elevated temperature results in low resistivity films, in the case of platinum this is not observed; in fact, deposition yield goes to zero as the substrate temperature is raised. The deposition of platinum at near grazing incidence of ion beam on a cleaved silicon surface has been observed. Such deposition differs from that of normal incidence, tending to form discrete islands at about 0.25 mu-m dimensions.