Investigation of ion beam mixing effects in Ta/Pd bilayers deposited on Si

Abstract

This paper presents a study of the effects of As + ion irradiation and vacuum thermal treatments on Ta/Pd bilayers on silicon. The layers were deposited by DC sputtering to the thickness of 60 nm (Pd) and 45 nm (Ta) on (111)Si wafers. The Ta/Pd/Si structures were then implanted with 300, 400 and 500 keV As + ions at room temperature (RT), to the doses from 0.5–1·10 16 ions cm −2. Thermal treatments of samples were performed in vacuum at 900°C, for 10 min. Characterizations were performed by Rutherford backscattering spectroscopy and X-ray diffraction. It was found that intermixing of the components at Ta/Pd and Pd/Si interfaces depends on the value of damage energy F D deposited by the incident ions at the interfaces. Ion bombardment at room temperature induces the formation of Pd 2Si phase with polycrystalline structure. Post-implantation annealing at 900°C made possible the growth of PdSi silicide. Then, the reaction of Ta with Si is enhanced by rapid silicon diffusion through already formed PdSi phase. Consequently, the formation of TaSi 2 and Ta 3Si silicides at the Ta/PdSi interface occurred.