| Laser programmable metallic interconnects have been widely used in semiconductor industry for both yield enhancement and customizable logic. In this work, the laser-induced vertical metallic link is thoroughly studied by both experiments and numerical simulations. Test chips were designed, fabricated and tested to investigate the laser energy and structural effects on the link formation. A LPROM-based integrated 4-point link resistance measuring circuit was designed and fabricated to optimize the laser conditions. A broad laser energy window is extracted, which shows great potential in commercial use. Finite element method is used to obtain the detailed information on the thermomechanical dynamics in the link during the laser radiation. The simulated results help to further optimize the link structure and laser conditions. Accelerated life tests were also conducted to predict the electromigration reliability of the links. A modified link structure is proposed to improve the electromigration resistance by using the “backflow” effect. Focused Ion Beam was used to cross section the chips and find the failure mechanisms. Finally, several potential implementations of the laser link are discussed in both digital and analog circuits. |
