Phase transformations in Ta-Si system induced by compression plasma flow

In this study, the effect of a dense compression nitrogen plasma flow on a microstructure and the elemental and phase compositions of a "tantalum layer-silicon substrate" system is investigated. Pre-deposited tantalum thin films (similar to 2 mu m thick) on Si(1 1 1) and Si(1 0 0) substrates were exposed to a single plasma pulse or to a series of pulses. The power density absorbed by the target, plasma pulse duration and discharge current were 1.2 GW/m(2), 100 mu s and 80 kA, respectively. The temperature field distribution and its time evolution were approximately simulated. SEM and EDX analyses revealed the presence of tantalum-rich domains consisting of nano-sized particles and spherical multilevel structures. X-ray diffraction analysis showed the formation of crystalline hexagonal tantalum-rich silicides and tantalum nitride. A mechanism explaining the structural changes and phase transformation of the Ta/Si system is proposed.