4908226 Selective area nucleation and growth method for metal chemical vapor deposition using focused ion beams

Abstract

A method for depositing metallic lines on an IC chip (52) or mask is described using a focused ion beam (FIB) (44) with a much lower ion dosage than previously required, on the order of 1014-1015 ions/cm2. A substrate (32) is scanned with the FIB (44) to produce a series of nucleation sites (46) on the substrate surface (42). These nucleation sites (46) can be in an adlayer (42) or can be produced by lattice damage or sputtering directly in the substrate material (32). The substrate (32) is then exposed to a source gas containing the material to be deposited, while heated to a temperature slightly less than the spontaneous thermal decomposition temperature of the source gas. This results in a well-defined line of materials being deposited from the source gas along the line (50) defined by the nucleation sites (46). The ratio of the spontaneous activation energy to the autocatalytic activation energy for the gases is preferably at least about an order of magnitude, and the FIB (44) is preferably moved in multiple scans across the desired line (50). In a particular embodiment both the adlayer (42) and source gas comprise iron pentacarbonyl, an ion dosage of 3x1014 ions/cm2 is used, and the substrate (32) is heated to approximately 130°C. The ion dosage is low enough that the system is compatible with other FIB processes, such as lithography, implantation and sputtering. Applications include the fabrication and repair of both ICs (52) and masks.