Control of the formation of ultrathin CoSi2 layers during the rapid thermal annealing of Ti/Co/Ti/Si(100) structures

Abstract

The initial Ti(8 nm)/Co(10 nm)/Ti(5 nm) structures formed on the Si(100) substrate by magnetron sputtering were subjected to two-stage rapid thermal annealing (RTA) in the nitrogen ambient. The samples of the structures were controlled using the time-of-flight SIMS, the Auger spectroscopy, scanning electron microscopy, X-ray dispersion microprobe analysis, and measurements of the layer resistance at each stage of annealing. At the RTA-1 stage (550°C, 45 s), a sacrificial layer formed on the surface. This layer consisted of the titanium (oxy)nitride coating, into which the residual impurities (O, C, and N) were forced out, and the transient Co-Si-Ti(TiO,TiN) layer with a high cobalt content and a low (trace) titanium content. After the selective removal of this sacrificial layer, the surface composition corresponded to monosilicide CoSi, which transformed into the highly conductive CoSi2 phase at the RTA-2 stage (830°C, 25 s).