Thermal and pulsed laser induced surface reactions in Ti/Si(001) interfaces studied by spectromicroscopy with synchrotron radiation

Abstract

Thin titanium silicide layers, produced by thermal or ultraviolet (UV) and visible pulsed laser annealing of Ti films deposited on Si substrates, have been studied by synchrotron radiation scanning photoemission spectroscopy (SR-SPEM) with lateral resolution of 0.12 μm. The evolution of the Ti 2p, Si 2p, and valence band spectra were used as fingerprints for the occurring morphological changes and interfacial reactions. For thermal processes the Ti films were deposited through a mask and by performing spectromicroscopy across the edge of the Ti patch the influence of the film thickness on the interface reaction was probed. The advancement of the interfacial reaction as a function of the annealing temperature was studied as well. The three components in the Si 2p spectra with chemical shift of −0.76, −0.50 and −0.18 eV, observed after thermal annealing at 650 and 850 °C were attributed to TiSi, C49 TiSi2, and C54 TiSi2, respectively. For the laser treated Ti/Si interfaces SPEM was successfully used to map the lateral distribution of these silicide phases formed within the laser irradiated region. In all cases the laser beams were focused and the photon density values were chosen to limit the temperature rise below the Si and Ti melting thresholds. We found that in the external region of the laser spots where the local temperature does not exceed 500 °C the dominating C49 TiSi2 phase coexists with some TiSi, whereas in the hottest central region the formation of C54 TiSi2 is favored. The similarity of the lateral distribution and the chemical phases formed within the laser spots obtained using UV and visible radiation confirmed that the local laser-induced temperature rise controls the interfacial processes, whereas the radiation wavelength plays a negligible role.