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

Copper alloyed with small amounts of aluminium or magnesium has recently be en suggested as a promising material for interconnect applications in silic on integrated circuits. This work reports the results of the investigation of the electrical (capacitance-voltage and current-voltage) stability of th e metal-oxide-semiconductor capacitor made with copper-0.5 at.% aluminium a nd copper-2 at.% magnesium as metal, deposited on thermally oxidized silico n substrates. The effect of thermal treatment in vacuum ambient before and/ or during the electrical testing was investigated. The resistance to oxidat ion of these alloys was also investigated. The results show that copper mag nesium, after a thermal treatment of 350 degrees C or higher, produces a pa ssivating layer at the interfaces that has excellent corrosion resistance a nd 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 thes e alloys, particularly copper magnesium, will form suitable interconnects w ithout the need of a diffusion barrier on SiO2 used as interlayer dielectri c. (C) 1998 Elsevier Science S.A. All rights reserved.