Ultrathin Ni silicide contacts on Si and SiGe formed with multi thin Ni/Al layers

We present the formation of very thin and uniform Ni silicide contacts on Si and strained SiGe using multi thin Ni/Al layers. Epitaxial Ni(Al_1-xSi _x)₂ layers are achieved on Si with a layer thickness from 14 nm to 33 nm. The contacts show a lower Schottky barrier than NiSi. The incorporation of a small amount of Al slightly changes the Schottky barrier compared to pure NiSi₂. Using Ni/Al multilayers allows formation of very thin and uniform Ni(Al)SiGe layers on SiGe. Best results Ni(Al)SiGe layers were obtained at 400°C with 20% Al. These layers show a Ni₅(SiGe)₃ phase. After silicidation the compressive strain in the remaining SiGe layer is still conserved, providing uniform contacts on high hole mobility SiGe layers.