Determination of metal/Si contact temperature during electrical current stressing

Interconnect reliability of very-large-scale-integrated (VLSI) circuits is a temperature-sensitive issue. However, it is extremely difficult to measure the temperature at a tiny contact using conventional methods. In this study a method of measuring contact temperature under electrical current stressing is devised using typical Kelvin test structures together with our special designed Seebeck coefficient test structures. The Ni/Si contacts on both p⁺-Si and n⁺-Si with a contact size of 10×10 μm² were examined using this method. When applying a current density of 10⁴ A/cm² through the contacts, the contact temperature is found to increase as much as by 20°C. The influences of substrate temperature and stressing current on the Ni/Si contact resistance are also discussed.