Laser linking of metal interconnect: Linking dynamics and failure analysis

A novel method of using a laser to connect two adjacent lines on the same level of metallization in integrated circuits was previously developed with programmable gate array applications and customized chips in mind. This work reports a study of failure mechanisms in the laser linking process. Experiments relating critical processing parameters (laser power and target alignment) to the visual failure modes were performed. A focused ion beam (FIB) was used to cross section and image failed links. The images were compared with previously published linking models. Finite element analysis (FEA) was used to simulate laser absorption and subsequent thermal diffusion, and to justify a simple model defining the process window for laser linking. The research correlated theoretical predictions for the failure modes with the critical processing parameters.