Focused ion beam fabrication of microelectronic structures

One of the most successful applications of focused ion beams has been the deposition of submicrometer conductors for integrated circuits. Our work has concentrated on demonstrating new materials and on studying the fundamental mechanisms of the deposition and milling processes. One of the important results has been the first demonstration of ion induced copper deposition from a new precursor gas. Copper is being considered a successor to aluminum in integrated circuits, and our copper had the lowest resistivity of any material produced by room temperature focused ion beam deposition. We have also studied the ion induced deposition of gold and tungsten as a function of angle of incidence as well as the milling of Si, SiO2, W, and Au. These processes are also important for the repair of lithography masks. A Monte Carlo model based on collision cascades has been developed for the fundamental mechanism for ion induced deposition and tested against measurements of deposition yield of Au for various ion energies and noble gas Ion species. The deposition appears to be substrate mediated and fits the collision cascade model. The dependent of milling and deposition as a function of ion incidence also appears to fit this model.