Electron beam induced deposition of low resistivity platinum from Pt(PF3)4

The authors have deposited Pt from Pt(PF3)4 using a focused 10keV electron beam (scanning electron microscopy) in an FEI 620 dual beam system and measured the resistivity and composition of the deposits. To measure resistivity, lines of Pt were deposited across four gold fingers and the cross-sectional area of the lines was measured by focused ion beam sectioning. The resistivity varies between about 30 and 650μΩcm and is orders of magnitude lower than the resistivity achieved by e-beam-induced deposition using the usual organometallic precursor, (methylcyclopentadienyl) trimethyl platinum. In general, the higher the beam current the lower the resistivity. They have used wavelength dispersive x-ray analysis to measure the composition of rectangles deposited with various beam currents. Typical at.% values of (Pt:P:F) are 81:17:2 and 58:32:10. Minimum linewidth that they have deposited is 80nm, and with a stationary beam of 2.8nA they have deposited a pillar of 135nm in diameter. They have also deposited Pt structures on freestanding carbon nanotubes and have used the deposits to contact nanofibers. Electron-beam-induced deposition of a “good” metal is particularly useful in geometries where standard lithography is awkward, such as making contacts to fibers or nanotubes randomly dispersed on a surface or freestanding.