The role of N in the resputtering inhibition of Si in W–Si–N reactively sputtered thin layers

Abstract

W–Si–N thin films were synthesized by reactive sputtering of W5Si3 target in an Ar∕N2 mixed atmosphere. The nitrogen atomic concentrations within the films ranged between 0 and 60at.%, as revealed by Rutherford backscattering measurements. At low nitrogen atom fluxes an intense Si resputtering was observed, leading to the formation of a W-rich layer with respect to target composition. The characterization of plasma parameters during the deposition, carried out with the help of a Langmuir probe, suggests that the Ar neutral atoms reflected by W atoms of the target are the main responsibilities of Si resputtering with respect to charged species, whose resputtering effect is less important. The inhibition of this phenomenon takes place with growing nitrogen concentration. The preferential formation of Si–N bonds with respect to W–N bonds was unveiled by both x-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. This also justifies the inhibition of Si resputtering. A comparison with literature data concerning W–Si–N systems sputtered at different plasma conditions was performed in order to highlight the influence of plasma parameters on the composition of the layers.