INFLUENCE OF ARSENIC ION-BEAM MIXING ON PALLADIUM SILICIDE FORMATION

In this paper we present a study of atomic mixing of palladium thin films on silicon, induced by ion implantation of arsenic ions. Palladium thin films were deposited by d.c. sputtering to a thickness of 100 nm. The substrates used were n-Si(111) wafers. After deposition the samples were implanted with 350 keV As+ ions. Ion implantations were carried out to doses from 1 x 10(14) ions cm-2 to 1 x 10(16) ions cm-2. Thermal treatments of samples, before and after ion implantation, were performed in vacuum (1 x 10(-5) mbar) at 400-degrees-C. Structural changes were analysed by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Ion bombardment at room temperature induced the formation of a Pd2Si phase with a polycrystalline structure. For the dose of 1 x 10(16) ions cm-2 the formation of Pd2Si was completed. Post-implantation thermal annealing of samples made possible the growth of relatively large Pd2Si grains with (002) preferred orientation. Our results show that the high concentration of defects induced by ion bombardment at metal-silicon interface enables the chemical reaction of Pd2Si formation.