Electromigration resistance of copper interconnects

Abstract

Copper has been suggested as a promising interconnect material for ULSI applications, because of the low resistivity of copper compared to aluminum. Due to decreasing interconnect and contact dimensions, a high electromigration resistance of the metallization material is required. Electromigration tests were performed in the course of the european COIN project on copper interconnects with linewidths between 1 and 4 μm and different sample preparations. The copper was deposited by CVD or PVD methods. Patterning was done by ion milling or RIE. TiN or TiW were used as a barrier. Tests were performed at wafer level and package level in the temperature range from 170°C to 250°C and current densities from 2 MA/cm 2 to 15 MA/cm 2. Activation energies between 0.60 and 1.00 eV were determined depending on the deposition and patterning method and the used barrier. A comparison between the different copper samples and a standard AlSiCu is presented showing a 10-fold improvement in lifetime.