Capacitance–voltage, current–voltage, and thermal stability of copper alloyed with aluminium or magnesium

Abstract

Copper alloyed with small amounts of aluminium or magnesium has recently been suggested as a promising material for interconnect applications in silicon integrated circuits. This work reports the results of the investigation of the electrical (capacitance–voltage and current–voltage) stability of the metal–oxide–semiconductor capacitor made with copper–0.5 at.% aluminium and copper–2 at.% magnesium as metal, deposited on thermally oxidized silicon substrates. The effect of thermal treatment in vacuum ambient before and/or during the electrical testing was investigated. The resistance to oxidation of these alloys was also investigated. The results show that copper magnesium, after a thermal treatment of 350°C or higher, produces a passivating layer at the interfaces that has excellent corrosion resistance and very stable behavior in terms of capacitance–voltage and current–voltage measurements. Copper aluminium performed adequately, much better than pure copper but was inferior to copper magnesium. It may be concluded that these alloys, particularly copper magnesium, will form suitable interconnects without the need of a diffusion barrier on SiO 2 used as interlayer dielectric.