Focused ion beam induced deposition of platinum

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Abstract
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 μΩ 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 μm long line. The minimum linewidth achieved so far is 0.3 μm. 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 μm dimensions.

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