Activation energy in the early stage of electromigration in Al-1% Si/TiN/Ti bamboo lines

Abstract
The activation energy of electromigration in 'bamboo'-type, passivated Al-1% Si/TiN/Ti lines was determined by means of high resolution resistance measurements at wafer level. Both the very early stages, with a nonlinear behaviour of the resistance, and the subsequent stages, characterized by an approximately constant rate of resistance change, were analysed with an existing model that correlates electromigration and mechanical stress evolution. An activation energy could be extracted only in the phase of linear resistance increase, where a value of 0.95 eV was found. Diffusion at the interface between Al-Si and the barrier metal or the passivation could be responsible for this value of the activation energy.