Improved electromigration test techniques of layered metal structures at wafer level

Abstract

The current constant stress (J-constant) technique is useful for evaluating the resistance rise, but can not evaluate "n" values because of metal temperature scattering among samples. Two modified Jc techniques are advised. By controlling the metal temperature at t(stress)=0 within /spl plusmn/1/spl deg/C of the target temperature, the "temperature-controlled" J-constant technique can evaluate n values efficiently. By monitoring the power and adjusting the stress current, the power-constant technique can reduce excess joule-heating and keep the metal temperature constant during stress, and smaller n values are obtained.