Abstract
With the evolution of VLSI process technology, continuous scaling of integrated circuit(IC) leads to increasing density of integrated circuits(IC) regime. High current density and current crowding phenomenon associated with the scaling may cause severe reliability problems. In the experiment, we modulate the Cu/Ta contact resistance by using hydrogen plasma for Ta surface pretreatment and explore the effect of contact resistance on current crowding behavior in Cu metallization. The samples used to study the influence of current density and surface pretreatment on the electrical/thermal properties of Cu/Ta contacts were prepared by conventional photolithography technique. A four-terminal Kelvin test structure were employed to measure the resistance of the contacts which have the contact size ranging from 4×4μm2 to 20×20μm2. It is found that the contact resistance is strongly affected by surface pretreatment conditions. Hydrogen plasma pretreatment was able to reduce the contact resistance significantly. Furthermore, the contact resistance was also affect by applied current and temperature, which decreased with increasing temperature and applied current. In the part of simulation, an commercial software, FlexPDE, were utilized to analyze the current distribution in Blech test structure. The simulation shows that the maximum current flowing into Cu strip decrease as the contact resistance increases. Besides, high contact resistance tends to spread out the current and reduce current crowding.