Abstract
The latest IC modification requirement is to decrease the resistivity of Focused Ion Beam (FIB) deposits, especially deposits within a FIB machined hole. The resistivity of platinum conductor deposited by FIB within a hole is much greater (5000-50000 μΩ-cm) than that deposited on a surface (~200 μΩ-cm) (1). Auger analysis of surface deposited platinum conductor gives the composition ratios as ~ 50% platinum, ~34% carbon, ~15% gallium and ~1 % Oxygen. The escape solid angle of the organic carrier is much less from a hole than from a surface; therefore, we find more of the non-conductive organic material is trapped inside the hole which increases the fill resistivity. With its planarization and multiple metal levels, advanced IC process technology forces contact to lower level metal to be through high aspect ratio holes. To make a low resistance contact through such a hole, deposited material must have a high ratio of platinum to carbon and Oxygen. An improved technique is needed to remove the organic carrier molecules and deposit material containing this higher platinum percentage. The way to achieve such deposition is to adjust gas arrival rate and beam current to produce a deposition rate that allows sufficient time for the organic carrier molecules to escape. Using this method, we can to obtain fill resistivity of about 1000-2500 μΩ-cm within high aspect ratio holes. This paper discusses in detail the technique to achieve such low resistivity in high aspect ratio holes. On the surface where space is not so limited, a greater deposition rate yields shorter times to resistance as well as better step coverage, but within a hole a lower resistivity material is needed to result in good conductance to lower level metal.
