Energy effect of the laser-induced vertical metallic link

In this paper, the energy effect of the laser vertical metallic link is inv estigated from a microscopic point of view through experimental observation s and simulations. Sample structures that were irradiated under different l aser energies were cross-sectioned and observed using a FIB/ SER-I dual-bea m system. Failure criterion at the high energy level was defined by excessi ve material loss in the lower metal (metal 1) and passivation cracking, Mic ro-images also suggest that, for an optimal link structure, the upper metal (metal 2) opening should be larger than the lower metal linewidth consider ing the dielectric-step-induced lens effect, Taking into account both measu red electrical resistance and observed voids in the lower metal, the normal ized energy process window is defined to be the absolute energy range divid ed by the average energy, For the structures with 1-, 2-, 3-, and 4-mum lon er metal linewidths, the relative process windows are 0.83, 0.87, 0.9, and 0.96, respectively, Simulations also revealed consistent results with the experimental observations, which is a monotonically decreasing trend of rel ative energy process windows for more scaled links. A simple equation to ev aluate the spot size of the laser beam fur various link structures is prese nted. These results demonstrate the application of commercially viable vert ical linking technology to VLSI applications.