Anomalous scaling effect of tungsten/titanium nitride/titanium to silicon electrical contact resistance for subquarter micron microelectronic devices

This paper reports the anomalous scaling effect of tungsten/titanium nitride/titanium to (a) n + and (b) p + silicon electrical contact resistance in dynamic random access memory (DRAM) devices, upon post heat treatment following rapid thermal silicidation annealing. The electrical measurements on contacts of sizes ranging from 0.54 mum to 0.18 mum reveal that the increase in resistance becomes larger as the contact size decreases. Transmission electron microscopy (TEM) results show that the silicide film agglomeration proceeds more severely as the contact size decreases. To explain the size-dependent degradation of the contact resistance, numerical simulation of the shape evolution of the silicide film is performed. The results show that the poor film coverage, especially at the edge, accelerates the reduction rate in contact area.